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Hi, I'm Danny Trejo, and I play Uncle Machete in the blockbuster movies Spy Kids and Spy

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Kids 2.

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As super spies, the Spy Kids have to use all kinds of exciting gizmos and gadgets to help

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save the world.

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But the real excitement begins in the classroom, as you learn how those gizmos and gadgets

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really work.

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So you won't want to miss the next big adventure, as the Treehouse Detectives use science, math

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and technology to reveal the secrets of simple machines, in order to help Jacob back in the

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treehouse.

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You can see it all in this episode of Nassau Sci-Files, The Case of the Powerful Pulleys.

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Nassau Sci-Files

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Nassau Sci-Files

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Don't forget to answer the following questions.

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What is energy?

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What does it mean to do work?

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What are simple machines?

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When you see this icon, the answer is near.

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Nassau Sci-Files

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Check this out.

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Jacob, watch out!

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Jacob?

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Jacob?

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You got gaffed!

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Nassau Sci-Files

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The doctor says I'll have to wear this cast for six to eight weeks.

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I'm sure it's tough being around in a cast.

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Yeah, I guess you have to take it nice and easy.

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Well, getting around is still okay.

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I really miss being in the treehouse.

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You are not climbing up into the treehouse.

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He's right, Jacob.

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Climbing into the treehouse would be a bad idea.

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I'm not going to climb into the treehouse.

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But you guys don't know what it's like being stuck in this cast.

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The treehouse is like my second home.

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Maybe we can figure out a way to get you back into the treehouse without climbing the ladder.

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You might be on to something, Bianca.

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Stop joking, you guys.

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You're getting my hopes up.

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We're not joking.

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After all, we are the treehouse detectives.

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It might take a little while, but we can solve the problem.

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I can't wait to get back into the treehouse.

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Don't worry, Jacob.

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I'm sure we'll have you back in the treehouse in no time at all.

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This problem may be tougher than we thought.

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Let's brainstorm.

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Maybe we could use a rope to pull Jacob up.

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Or maybe a trampoline.

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A trampoline? That's silly.

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Remember, there's no criticism when you brainstorm.

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What about lowering the treehouse?

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Or we could carry him up.

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How much does Jacob weigh?

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Probably about 90 pounds.

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Well, that's not too much.

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You must try my idea of lifting him with a rope.

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Let's give it a try.

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Can we do this later this afternoon?

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Bianca and I are going to Sandy Bottom Nature Park

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with my sister's Girl Scout troop.

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Dr. D is doing some physics experiments.

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Sure. See you this afternoon.

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Bye.

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It takes energy to do work.

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Energy comes in a variety of forms.

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The powder in this funnel has potential energy.

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It's changed into heat energy when I blow it through this flame.

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If I do work and use my energy to stretch this flame,

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the energy is stored as elastic potential energy.

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And when I let go,

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the energy is changed into energy of motion,

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or kinetic energy.

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Finally,

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Flexiglas did the work to stop the tomato.

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It takes a lot of work to lift this 25-kilogram anvil.

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I have to overcome the pull of gravity.

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The anvil now has a lot of gravitational potential energy.

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This poor cantaloupe will be smashed.

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When I release it,

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This poor cantaloupe will be smashed.

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When I release the energy by letting go.

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Hi, Dr. D.

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That was a great show.

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I really liked the experiments.

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Thanks.

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By the way, are you working on any projects?

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Well, Jacob has broken his foot,

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so we're trying to figure out a way to get him back into the treehouse.

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We think we can lift him with a rope,

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if we all work together.

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Let's talk a little bit about work.

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First you have to have a force, a push or a pull.

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The force alone is not enough.

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To do work, the force must be applied through a distance.

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Here, hold onto this anvil for me.

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Sure, but why?

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Getting tired yet?

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You bet.

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Because you haven't moved the anvil,

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you haven't done any work.

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Doing work and getting tired are not necessarily the same thing.

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Can we put this thing down?

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Of course.

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Now, with the slingshot,

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I did work when I pulled on the strap

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and moved it back about one meter.

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When I let go of the strap,

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the slingshot did work on the tomato

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when it pushed it forward and sped it up.

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I love the slack.

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Now, with the 25-kilogram anvil,

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I had to supply a force of about 55 pounds,

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going against gravity as I picked it up.

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The higher I lifted the anvil,

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the more work I did

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and the more gravitational energy the anvil had.

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Then the anvil must have had a lot of energy

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because it sure crushed the cantaloupe.

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But Jacob is heavier than 55 pounds.

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Does that mean it would take more work to lift him?

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Yes, that's right.

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Since work is equal to force times distance,

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increasing either the force or the distance will require more work.

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You said it took energy to do work.

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So where did the energy come from to lift the anvil?

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The energy came from the corn flakes I had for breakfast this morning.

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Corn got its energy from the sun.

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It's going to take a lot of energy to lift Jacob into the treehouse.

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I think it's going to take all our energy to do the job.

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Thanks, Dr. D.

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You're welcome.

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Bye.

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Bye-bye.

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Wow, exactly 3.5 meters.

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It's harder than I thought.

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My dad had some rope that we can use to lift Jacob.

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Great, let's lower it down.

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Maybe we could attach it to the test dummy down below.

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KCNN is coming on.

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Good morning, everyone.

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I'm Ted Toombs.

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Our top story, Kids Science News Network is getting a facelift.

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The next time you see me, I'll be in the new and improved KSNN studio.

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Okay, let's get him out of here.

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Hey, stop that.

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Cut it out.

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Put me down.

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I'm with Patio Furniture, the studio construction supervisor.

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Patty, what can you tell us about the redesign?

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We're taking out all the old stuff and replacing it with new stuff, I am.

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We're going totally techno here.

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We'll have the digital interactive weather board over there, the remote satellite.

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Hey, you're not touching with that new skunk.

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Sport super slow motion system over here, and the new.

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Careful with that dynamite.

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Hyper speed wire service feeds in that form.

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Well, things are certainly changing around here.

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Be sure to join Patty and the KSNN news crew to learn more about our jobs

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and why we love them at the upcoming Career Day.

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Until next time, I'm I Am Listening for KSNN.

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The new studio should be awesome.

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You bet.

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Is anyone going to Career Day?

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Actually, I'm working on a presentation for Career Day.

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Aren't you a little young to be thinking about a career?

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You're never too young to do research.

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That's true.

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My mom works for SWE.

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I've always been interested in engineering.

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What's SWE?

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SWE stands for the Society of Women Engineers.

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I don't know what I want to be when I grow up, but it's important to know what's out there.

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You're right. Maybe we can help you with your presentation.

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Don't forget, we have an engineering problem of our own.

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That's true.

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I've been thinking about our hypothesis.

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We could use a rope to pull Jacob back into the tree house.

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Well, I better go attach rope to our test dummy.

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We were wondering what all the sandbags were doing at the bottom of the tree.

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They look heavy. Are you sure you can lift them?

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It weighs about 90 pounds, which is almost 41 kilograms.

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If we can lift it, Jacob should be no problem.

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Okay. We're all set down below.

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Well, let's get started.

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Are you ready to pull?

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Yep. On the count of three.

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One, two, three.

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Can you two give us a hand?

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Thanks.

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Wow. It's still hard to pull.

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Are you sure this is only 41 kilograms?

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This isn't working.

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Okay. Let's lower him down.

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That didn't work like I thought it would.

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We need a new hypothesis.

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You're right. We didn't think through the problem very carefully.

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I guess we jumped to conclusions too quickly.

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We can do this. We just need to get organized and get back to the basics.

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The problem board.

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Okay. What do we know?

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We know we need to get Jacob into the tree house.

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And that it's too hard to pull him up with a rope.

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Dr. D told us that work requires force applied over a distance.

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And that takes energy.

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So, what do we need to know?

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We need to know an easier way to get Jacob up into the tree house.

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Right. There must be a machine that could help.

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Like an elevator or a crane.

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An elevator sounds great.

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I'm not sure what the power source is, but they are made to lift people.

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Maybe we could build a small elevator in the tree house.

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If we found a way to power the elevator, we could easily lift Jacob.

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I think we need to learn more about elevators.

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I'll check the internet.

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I'll see if I have something in my book bag.

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Yes. And check it out.

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Elisha Graves Otis invented the elevator in 1853.

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After developing a safety device for a lift platform.

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I didn't know elevators were that old.

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Guys, Otis Elevator has a website.

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I wonder if it's the same Otis.

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I bet it is.

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It says here that they design and install elevators all around the world.

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I'll email them and see if they can help.

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While you're on the internet, print out an extra get up and go sheet.

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You can go to the NASA Sci-Files website to do research and print out your own get up and go sheet.

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Hello. We're the tree house detectives and we need to learn more about elevators.

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Well, you've come to the right place.

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I'm Edith DeFrancesco, Vice President of Product Development here at Otis Elevator Company.

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Wow. That sounds interesting.

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Do you actually build elevators?

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Here at the test tower, we test elevators for safety and efficiency.

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And I don't personally build elevators.

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Although as a mechanical engineer, I've worked on elevator designs.

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You're an engineer? I'm doing a report on engineers for career day.

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Great. I'll show you where we design and test our elevators.

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We have lots of engineers working on elevator design.

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This is our test tower.

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After we design the elevators, we bring them here to test them to see how they will work when they're installed.

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How do elevators work?

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Elevators are driven by electric motors.

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And on the motor shaft is a pulley called a shiv.

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Over the shiv hang steel cables.

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It's basically a box on a rope.

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On one end of the cable is the elevator car which carries the people.

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And on the other end is the counterweight.

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What's a counterweight?

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A counterweight is a steel frame full of weights.

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And it balances the weight of the elevator car and the people in it.

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So that it takes less force to move the elevator.

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How does it reduce the amount of force needed?

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Think of it like a balance scale.

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The force needed to turn the shiv is related to the difference between the weight of the car with the people in it and the weight of the counterweight.

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The closer those two are in weight, the more balanced the system is and the easier it is to turn the shiv.

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How does an elevator go up and down?

257
00:12:26,400 --> 00:12:29,400
Well, when the motor turns, the shiv rotates.

258
00:12:29,400 --> 00:12:31,400
The cables stay on the shiv in these grooves.

259
00:12:31,400 --> 00:12:37,400
And with the friction between the cables and the shiv, the cables move with the shiv when it rotates, making the elevator go up and down.

260
00:12:37,400 --> 00:12:40,400
It sounds like friction is a good thing to have in an elevator.

261
00:12:40,400 --> 00:12:43,400
Yes, we call it traction and it's very important.

262
00:12:43,400 --> 00:12:46,400
We don't need a very big elevator for our treehouse.

263
00:12:46,400 --> 00:12:48,400
Do elevators come in different sizes?

264
00:12:48,400 --> 00:12:52,400
Yes, they can be as small as a dumbwaiter, about a half a meter by a half a meter.

265
00:12:52,400 --> 00:12:54,400
How big can an elevator be?

266
00:12:54,400 --> 00:12:56,400
Some elevators are as big as a truck.

267
00:12:56,400 --> 00:12:58,400
They're used to carry freight containers at seaports.

268
00:12:58,400 --> 00:13:03,400
But a typical commercial elevator is about a meter by two meters and carries 10 or 12 people.

269
00:13:03,400 --> 00:13:05,400
Designing an elevator seems like a lot of work.

270
00:13:05,400 --> 00:13:07,400
It sounds like a lot of fun.

271
00:13:07,400 --> 00:13:09,400
It has its ups and downs.

272
00:13:09,400 --> 00:13:12,400
Thanks, Mrs. DeFrancesco. We've learned a lot about elevators.

273
00:13:12,400 --> 00:13:15,400
You're welcome. And if you have any more questions, just give me a call.

274
00:13:15,400 --> 00:13:16,400
Bye.

275
00:13:16,400 --> 00:13:17,400
Bye.

276
00:13:17,400 --> 00:13:18,400
Bye.

277
00:13:18,400 --> 00:13:21,400
Wow, I never knew elevators were so cool.

278
00:13:21,400 --> 00:13:27,400
If we're going to build an elevator, we'll need an electric motor, a shove, a shaft, a counterweight, and an elevator car.

279
00:13:27,400 --> 00:13:30,400
Boy, building an elevator sounds expensive.

280
00:13:30,400 --> 00:13:35,400
Not to mention complex. There has to be an easier way to get Jacob up into the treehouse.

281
00:13:35,400 --> 00:13:37,400
What about a ramp?

282
00:13:37,400 --> 00:13:39,400
What, like a bike ramp?

283
00:13:39,400 --> 00:13:41,400
Like that one over there.

284
00:13:45,400 --> 00:13:48,400
Oh, hey, I just got an email from Bianca and Anthony.

285
00:13:48,400 --> 00:13:51,400
They said that they spoke to an engineer about elevators.

286
00:13:51,400 --> 00:13:54,400
That would be great for Bianca's career day presentation.

287
00:13:54,400 --> 00:13:59,400
They also said that an elevator would be too expensive for the treehouse.

288
00:13:59,400 --> 00:14:01,400
And we might want to think about a ramp instead.

289
00:14:01,400 --> 00:14:02,400
What kind of ramp?

290
00:14:02,400 --> 00:14:06,400
You know, ramps that make buildings more accessible to wheelchairs.

291
00:14:06,400 --> 00:14:10,400
Investigate use of ramp.

292
00:14:10,400 --> 00:14:16,400
I have a friend who uses a wheelchair. Maybe he can tell us about what it's like to use ramps.

293
00:14:16,400 --> 00:14:17,400
Let's dial him up.

294
00:14:17,400 --> 00:14:20,400
Hi, our friend Jacob just broke his foot.

295
00:14:20,400 --> 00:14:23,400
And he is learning a little bit about what it is like to be disabled.

296
00:14:23,400 --> 00:14:27,400
Oh, that's too bad, but at least his foot will be well soon.

297
00:14:27,400 --> 00:14:31,400
He really wants to come into the treehouse, but it's not wheelchair accessible.

298
00:14:31,400 --> 00:14:33,400
Have you experienced that?

299
00:14:33,400 --> 00:14:38,400
Yes, a lot of places are not built to accommodate people who are in wheelchairs or have other disabilities.

300
00:14:38,400 --> 00:14:43,400
But today, public places are required by law to be accessible to everyone.

301
00:14:43,400 --> 00:14:48,400
I didn't know that there were laws that require buildings to be accessible to everyone.

302
00:14:48,400 --> 00:14:52,400
What can you do to make buildings accessible to people with disabilities?

303
00:14:52,400 --> 00:14:58,400
Well, a lot of buildings use simple machines, such as a ramp, which is an inclined plane.

304
00:14:58,400 --> 00:15:01,400
Some use elevators, but they are a little more complex.

305
00:15:01,400 --> 00:15:04,400
We need to keep it simple. What is a simple machine?

306
00:15:04,400 --> 00:15:11,400
A simple machine is a device that makes work more convenient by changing the speed, direction, or amount of force.

307
00:15:11,400 --> 00:15:13,400
There are six simple machines.

308
00:15:13,400 --> 00:15:19,400
Inclined plane, levers, wheel and axle, wedge, pulley, and a screw.

309
00:15:19,400 --> 00:15:25,400
We were thinking that a ramp might be the answer to our problem, but we didn't know that they were simple machines.

310
00:15:25,400 --> 00:15:27,400
Are there any requirements for ramps?

311
00:15:27,400 --> 00:15:35,400
If you want to build Jacob a ramp to get into the treehouse, the ramp will need to be built at a 12 to 1 ratio.

312
00:15:35,400 --> 00:15:38,400
That really helps. It gives us a lot to think about.

313
00:15:38,400 --> 00:15:39,400
See you later.

314
00:15:39,400 --> 00:15:43,400
I wonder if there are any other simple machines we need to use to solve our problem.

315
00:15:43,400 --> 00:15:45,400
We need to do more research.

316
00:15:48,400 --> 00:15:53,400
So what's up? How much work will it take to get Jacob into the treehouse?

317
00:15:53,400 --> 00:15:56,400
How will engineering help the treehouse detectives?

318
00:15:56,400 --> 00:15:58,400
Is the ramp the solution to the problem?

319
00:15:58,400 --> 00:16:02,400
Find out next time in The Case of the Powerful Pulleys.

320
00:16:03,400 --> 00:16:06,400
Be sure to answer the following questions during the show.

321
00:16:06,400 --> 00:16:11,400
What is the difference between potential and kinetic energy?

322
00:16:11,400 --> 00:16:16,400
How can pulleys help lift the space shuttle?

323
00:16:16,400 --> 00:16:20,400
How does a pulley make lifting objects easier?

324
00:16:20,400 --> 00:16:23,400
When you see this icon, the answer is near.

325
00:16:24,400 --> 00:16:27,400
Wow, 3.5 meters is much higher than I thought.

326
00:16:27,400 --> 00:16:30,400
Yes, this will be some incline plane.

327
00:16:30,400 --> 00:16:38,400
Let's see. If the incline plane is 3.5 meters high, at a 12 to 1 ratio, that would be...

328
00:16:38,400 --> 00:16:45,400
If the incline plane is 3.5 meters high, at a 12 to 1 ratio, that would be...

329
00:16:55,400 --> 00:17:01,400
With the correct slope, the incline plane would be about here, 42 meters.

330
00:17:01,400 --> 00:17:03,400
It would have to be a really big ramp.

331
00:17:03,400 --> 00:17:05,400
I think ramps are definitely out of the question.

332
00:17:05,400 --> 00:17:10,400
Well, there are other types of simple machines, and we need to know what they are and how they work.

333
00:17:13,400 --> 00:17:16,400
Maybe we could do an internet search on simple machines.

334
00:17:16,400 --> 00:17:18,400
We need to talk to more engineers.

335
00:17:18,400 --> 00:17:21,400
My mom talked to some engineers with her speed group. I'm sure they can help.

336
00:17:21,400 --> 00:17:23,400
Great, let's get to work.

337
00:17:25,400 --> 00:17:28,400
Oh, we just got an email from Dr. D.

338
00:17:28,400 --> 00:17:32,400
It says he wants to meet us at the circus later.

339
00:17:32,400 --> 00:17:34,400
I wonder what he wants.

340
00:17:34,400 --> 00:17:37,400
I'm curious, but it's Dr. D. and the circus. You know that'll be fun.

341
00:17:37,400 --> 00:17:41,400
I bet he can help. I'm sure he knows all about simple machines.

342
00:17:41,400 --> 00:17:44,400
I'll go check on Jacob, and let him know how we're doing.

343
00:17:49,400 --> 00:17:53,400
Look, Dr. D. is balancing up on that big ball. I hope he doesn't fall off.

344
00:17:53,400 --> 00:17:57,400
Hi, Dr. D. It looks like you're having a great time.

345
00:17:57,400 --> 00:17:59,400
Hey, I'm right there!

346
00:18:05,400 --> 00:18:08,400
There's a lot of science here at the circus center.

347
00:18:08,400 --> 00:18:12,400
Science? I never knew that there could be science at a circus.

348
00:18:12,400 --> 00:18:17,400
Sure there is. The circus is a great place to get some ideas to help you solve your problem.

349
00:18:17,400 --> 00:18:20,400
We're particularly interested in simple machines.

350
00:18:20,400 --> 00:18:26,400
Great. Right now they're using a teeter board, which is a lever with a fulcrum or rotational point in the middle.

351
00:18:26,400 --> 00:18:28,400
How does it work?

352
00:18:28,400 --> 00:18:30,400
Well, let's watch this.

353
00:18:35,400 --> 00:18:37,400
That was pretty neat.

354
00:18:37,400 --> 00:18:41,400
I noticed that two men jumped on the board, but only one flew into the air.

355
00:18:41,400 --> 00:18:46,400
Those two men that jumped are called pitchers. The one that flew up in the air is called a flyer.

356
00:18:46,400 --> 00:18:48,400
I should have guessed that one.

357
00:18:48,400 --> 00:18:51,400
After the pitchers jump, they have a lot of potential energy.

358
00:18:51,400 --> 00:18:55,400
It looked like the flyer went at least twice as high as the pitchers.

359
00:18:55,400 --> 00:18:59,400
Exactly. Two men have the same energy as one man twice as high.

360
00:18:59,400 --> 00:19:03,400
Exactly. Two men have the same energy as one man twice as high.

361
00:19:03,400 --> 00:19:06,400
The flyer also helps by pushing off the board.

362
00:19:06,400 --> 00:19:08,400
So the lever didn't create any energy.

363
00:19:08,400 --> 00:19:09,400
That's right.

364
00:19:09,400 --> 00:19:13,400
The lever changes the downward motion of the pitchers to the upward motion of the flyers.

365
00:19:13,400 --> 00:19:15,400
Correct. It's not magic.

366
00:19:15,400 --> 00:19:19,400
The teeter board just lets them transfer energy from the pitchers to the flyer.

367
00:19:19,400 --> 00:19:23,400
How would you like to experience the flying trapeze?

368
00:19:23,400 --> 00:19:25,400
That would be so cool.

369
00:19:25,400 --> 00:19:28,400
Now what does the flying trapeze have to do with energy?

370
00:19:29,400 --> 00:19:33,400
When you are way up there on the platform waiting, you have a lot of potential energy.

371
00:19:33,400 --> 00:19:37,400
Then when you grab the trapeze and swing down, you build up kinetic energy.

372
00:19:37,400 --> 00:19:41,400
And when you swing back again, you lose kinetic energy and pick up potential energy.

373
00:19:41,400 --> 00:19:45,400
Very good. So energy isn't being transferred like on the teeter board.

374
00:19:45,400 --> 00:19:50,400
It's just changing from potential energy to kinetic energy and then back again.

375
00:19:50,400 --> 00:19:54,400
That's why it's the acrobats on the aerial hoop. These guys are really something.

376
00:19:55,400 --> 00:19:59,400
Someone will have to do a lot of work to lift the hoop and the acrobat together.

377
00:20:01,400 --> 00:20:04,400
It looks really easy to pull them up. What are they using with the rope?

378
00:20:04,400 --> 00:20:06,400
It looks like they're using pulleys attached to the rope.

379
00:20:06,400 --> 00:20:10,400
I think this just might be the thing we need to pull Jacob up into the treehouse.

380
00:20:10,400 --> 00:20:13,400
This is great. We're making some real progress. Thanks, Dr. D.

381
00:20:13,400 --> 00:20:16,400
You're welcome. Let's see it by trapeze training.

382
00:20:17,400 --> 00:20:19,400
Let's summarize what we know.

383
00:20:19,400 --> 00:20:22,400
We know that work is force times distance and that it takes energy to do work.

384
00:20:22,400 --> 00:20:25,400
We know that levers change a downward motion to an upward motion.

385
00:20:25,400 --> 00:20:28,400
And that energy changes from potential energy to kinetic energy.

386
00:20:28,400 --> 00:20:31,400
And we also know that pulleys lift large objects more easily.

387
00:20:31,400 --> 00:20:33,400
Okay, so what do we need to know?

388
00:20:33,400 --> 00:20:35,400
We need to know more about pulleys.

389
00:20:35,400 --> 00:20:36,400
I'll bet Nassie uses pulleys.

390
00:20:36,400 --> 00:20:39,400
I'll email my mom and see if she's found any engineers that we can talk to.

391
00:20:39,400 --> 00:20:42,400
And don't forget to email Anthony and tell him what we've learned.

392
00:20:43,400 --> 00:20:46,400
And don't forget to email Anthony and tell him what we've learned.

393
00:20:46,400 --> 00:20:47,400
We're making progress.

394
00:20:47,400 --> 00:20:48,400
That's a great idea.

395
00:20:48,400 --> 00:20:51,400
And we gotta go because we don't want to miss our trapeze class.

396
00:21:06,400 --> 00:21:08,400
Hi, guys. How's the project going?

397
00:21:08,400 --> 00:21:10,400
Great so far. Thanks for your email.

398
00:21:10,400 --> 00:21:14,400
Your mom is friends with Mrs. Jones, an aerospace engineer here at NASA Langley Research Center.

399
00:21:14,400 --> 00:21:17,400
RJ's meeting her at the gantry this afternoon to talk about pulleys.

400
00:21:17,400 --> 00:21:18,400
That's great.

401
00:21:18,400 --> 00:21:20,400
He also said not to worry.

402
00:21:20,400 --> 00:21:23,400
He plans on getting plenty of information for your career day presentation.

403
00:21:23,400 --> 00:21:26,400
Speaking of career day, Kirsten N's coming on.

404
00:21:27,400 --> 00:21:30,400
I'm I Am Listening, live from my dressing room.

405
00:21:30,400 --> 00:21:33,400
During the construction, I'll be filing a series of special reports

406
00:21:33,400 --> 00:21:37,400
about how I personally redesign and overhaul my own dressing room.

407
00:21:37,400 --> 00:21:41,400
And I'm thinking, if this is as easy as it looks, I may just change careers.

408
00:21:42,400 --> 00:21:45,400
This isn't funny anymore. Get me down.

409
00:21:46,400 --> 00:21:49,400
Until next time, I'm I Am Listening for KSNN.

410
00:21:50,400 --> 00:21:52,400
I Am's presentation should be interesting.

411
00:21:52,400 --> 00:21:54,400
How's your report coming, Bianca?

412
00:21:54,400 --> 00:21:55,400
So far so good.

413
00:21:55,400 --> 00:22:00,400
I've researched engineering in general, and the engineer at Otis Elevator was very helpful.

414
00:22:00,400 --> 00:22:02,400
In a way, we're engineers for our pulley project.

415
00:22:02,400 --> 00:22:04,400
Right, but we still have a long way to go.

416
00:22:04,400 --> 00:22:06,400
Have you found anything on the Internet about pulleys?

417
00:22:06,400 --> 00:22:08,400
There's lots of information on the NASA website.

418
00:22:08,400 --> 00:22:11,400
It looks like Ms. Enix from Dryden can help us with pulleys.

419
00:22:11,400 --> 00:22:12,400
Let's dial her up.

420
00:22:14,400 --> 00:22:18,400
Hi, I'm Kimberly Enix, an aerospace engineer,

421
00:22:18,400 --> 00:22:23,400
working here at the Propulsion and Performance Branch at NASA Dryden Flight Research Center.

422
00:22:23,400 --> 00:22:26,400
Wow, an aerospace engineer.

423
00:22:26,400 --> 00:22:28,400
What does an aerospace engineer do?

424
00:22:28,400 --> 00:22:31,400
I do flight test research on different types of aircraft.

425
00:22:31,400 --> 00:22:32,400
What do you do?

426
00:22:32,400 --> 00:22:35,400
I do flight test research on different types of planes.

427
00:22:35,400 --> 00:22:38,400
We actually put our experiments on real jet engines,

428
00:22:38,400 --> 00:22:42,400
install the engines in experimental planes, and then we go out and fly them.

429
00:22:42,400 --> 00:22:46,400
That sounds really cool. Add that to the career list.

430
00:22:46,400 --> 00:22:49,400
We're doing a project, and we need to learn more about pulleys.

431
00:22:49,400 --> 00:22:54,400
We saw on the website that NASA uses pulleys to lift the Space Shuttle onto the back of a 747 plane.

432
00:22:54,400 --> 00:22:57,400
How can pulleys help lift the Space Shuttle?

433
00:22:57,400 --> 00:23:02,400
To lift the Space Shuttle, they use the mate-demate device known as the MDD.

434
00:23:02,400 --> 00:23:06,400
The MDD is this large gantry-like steel structure,

435
00:23:06,400 --> 00:23:10,400
where the Space Shuttle receives post-flight servicing

436
00:23:10,400 --> 00:23:14,400
and is prepared for the ferry flight back to NASA Kennedy Space Center.

437
00:23:14,400 --> 00:23:21,400
The MDD has two 100-foot towers that are connected at 80 feet by a horizontal structure.

438
00:23:21,400 --> 00:23:23,400
What does the horizontal structure do?

439
00:23:23,400 --> 00:23:29,400
It controls and guides a large lift beam that attaches to the Space Shuttle to raise or lower it.

440
00:23:29,400 --> 00:23:34,400
There are three large hoists, or pulleys, that are used to raise and lower the lift beam.

441
00:23:34,400 --> 00:23:37,400
Those must be some big pulleys.

442
00:23:37,400 --> 00:23:42,400
Yes, they are. The Shuttle can weigh up to 232,000 pounds,

443
00:23:42,400 --> 00:23:46,400
but each of the three pulleys has a 100,000-pound lift capability.

444
00:23:46,400 --> 00:23:52,400
Operating together, the total lifting capacity of the three pulleys is 300,000 pounds.

445
00:23:52,400 --> 00:23:57,400
But, for safety reasons, we don't exceed 240,000 pounds.

446
00:23:57,400 --> 00:24:01,400
Wow, that's about 120 times.

447
00:24:01,400 --> 00:24:03,400
You're good at math.

448
00:24:03,400 --> 00:24:07,400
There are also two equipment pulleys built into each tower at the 60-foot level.

449
00:24:07,400 --> 00:24:11,400
Each pulley is capable of lifting 10,000 pounds.

450
00:24:11,400 --> 00:24:15,400
Sounds like pulleys can lift a lot of weight and are pretty important at NASA.

451
00:24:15,400 --> 00:24:18,400
What happens to the Space Shuttle once it's lifted?

452
00:24:18,400 --> 00:24:25,400
The Space Shuttle is then placed on special mounts atop the fuselage of the NASA 747 Shuttle Carrier Aircraft.

453
00:24:25,400 --> 00:24:28,400
It is then flown back to the Kennedy Space Center.

454
00:24:28,400 --> 00:24:31,400
The Space Shuttle actually gets a piggyback ride.

455
00:24:31,400 --> 00:24:33,400
About how long does it take?

456
00:24:33,400 --> 00:24:36,400
Depending on the weather, it usually takes one to two days.

457
00:24:36,400 --> 00:24:38,400
Thanks, Ms. Enix. You've been a big help.

458
00:24:38,400 --> 00:24:42,400
You're welcome. Call if you need anything else, and good luck.

459
00:24:42,400 --> 00:24:44,400
Wow, that is so cool.

460
00:24:44,400 --> 00:24:47,400
I can't believe they lift the Shuttle with pulleys.

461
00:24:47,400 --> 00:24:50,400
If the pulleys can lift the Space Shuttle, I'm sure they could lift Jacob.

462
00:24:50,400 --> 00:24:55,400
I took a lot of notes. I'll enter them into the computer so Jacob and the others can check them out.

463
00:24:55,400 --> 00:24:58,400
And with RJ's notes, we should know a lot about pulleys.

464
00:25:00,400 --> 00:25:04,400
Hi, RJ. Bianca's mom said you'd be coming by. How can I help you?

465
00:25:04,400 --> 00:25:07,400
We need to learn more about pulleys. What exactly is a pulley?

466
00:25:07,400 --> 00:25:11,400
Well, a pulley is a simple machine. It's made from a rope and a wheel.

467
00:25:11,400 --> 00:25:13,400
It makes lifting objects easier.

468
00:25:13,400 --> 00:25:14,400
How does it do that?

469
00:25:14,400 --> 00:25:16,400
It changes the direction of the force.

470
00:25:16,400 --> 00:25:22,400
For example, if you're lifting a heavy object off the floor using a pulley mounted to the ceiling,

471
00:25:22,400 --> 00:25:25,400
you can pull down the rope instead of pushing up.

472
00:25:25,400 --> 00:25:28,400
Aren't you using the same amount of force needed to lift an object?

473
00:25:28,400 --> 00:25:32,400
Good question. Yes, you are, but it's easier to pull down than to push up.

474
00:25:32,400 --> 00:25:36,400
So how would I reduce the amount of force needed to lift a heavy object?

475
00:25:36,400 --> 00:25:40,400
If you add a second pulley and you support the load with two ropes,

476
00:25:40,400 --> 00:25:43,400
then you only need half of the force to lift it.

477
00:25:43,400 --> 00:25:47,400
What if you add a third pulley and support the load with three ropes?

478
00:25:47,400 --> 00:25:51,400
If you divide the weight of the object by the number of ropes supporting the load,

479
00:25:51,400 --> 00:25:54,400
then you can determine what kind of force you need to lift the object.

480
00:25:54,400 --> 00:25:58,400
Awesome. So what do you use pulleys for here at NASA Langer Research Center?

481
00:25:58,400 --> 00:26:03,400
As an aerospace engineer and a Level 3 manager of NASA's Aviation Safety Program,

482
00:26:03,400 --> 00:26:06,400
I use pulleys in crashworthiness research.

483
00:26:06,400 --> 00:26:08,400
What's crashworthiness?

484
00:26:08,400 --> 00:26:12,400
Crashworthiness is how well an aircraft protects occupants in a crash.

485
00:26:12,400 --> 00:26:17,400
A team of engineers and I conduct tests and analysis on materials,

486
00:26:17,400 --> 00:26:19,400
on aircraft structures and full-scale aircraft.

487
00:26:19,400 --> 00:26:21,400
Why is that important?

488
00:26:21,400 --> 00:26:25,400
In a real crash, it is very difficult to understand the damage because many things are destroyed.

489
00:26:25,400 --> 00:26:30,400
By conducting controlled crash tests, we can better understand what happens in a real crash,

490
00:26:31,400 --> 00:26:35,400
and then we can develop better designs that will protect the passengers.

491
00:26:35,400 --> 00:26:37,400
You crash real airplanes here?

492
00:26:37,400 --> 00:26:39,400
We sure do, right here at the gantry.

493
00:26:39,400 --> 00:26:41,400
What exactly is the gantry?

494
00:26:41,400 --> 00:26:45,400
The gantry is the Impact Dynamics Research Facility where we perform full-scale crash tests.

495
00:26:45,400 --> 00:26:49,400
It was also used by astronauts during the Apollo missions to practice landing on the moon.

496
00:26:49,400 --> 00:26:52,400
That's cool. How do you crash planes?

497
00:26:52,400 --> 00:26:55,400
A test vehicle is suspended from two swing cables, pulled back and released

498
00:26:56,400 --> 00:26:59,400
to allow the test vehicle to swing into the impact surface below.

499
00:26:59,400 --> 00:27:03,400
The swing cables are pyrotechnically separated from the vehicle just prior to the impact

500
00:27:03,400 --> 00:27:06,400
so that free flight conditions are established.

501
00:27:06,400 --> 00:27:09,400
Airplanes are really heavy. You must need a lot of pulleys.

502
00:27:09,400 --> 00:27:12,400
Actually, we only use one pulley, but it's a pretty big pulley.

503
00:27:12,400 --> 00:27:14,400
How much can you lift?

504
00:27:14,400 --> 00:27:19,400
We currently can only lift up to 30,000 pounds because that's the maximum capacity of the gantry's bridge.

505
00:27:19,400 --> 00:27:21,400
How can you lift 30,000 pounds?

506
00:27:21,400 --> 00:27:25,400
I run steel rope from the lifting device through the pulley and then attach it back to the bridge.

507
00:27:25,400 --> 00:27:28,400
The pulley is attached to the aircraft. This is called double hitching.

508
00:27:28,400 --> 00:27:30,400
30,000 pounds is a lot of weight.

509
00:27:30,400 --> 00:27:33,400
Yes, it is, but we don't need 30,000 pounds of force to lift it.

510
00:27:33,400 --> 00:27:37,400
With one pulley attached to the aircraft, you have two ropes supporting the load.

511
00:27:37,400 --> 00:27:40,400
Then you only need 15,000 pounds of force.

512
00:27:40,400 --> 00:27:43,400
Alfred and Jacob doesn't weigh 30,000 pounds,

513
00:27:43,400 --> 00:27:46,400
so I bet we could use pulleys to lift them with no problem at all.

514
00:27:46,400 --> 00:27:48,400
Thanks, Mrs. Jones.

515
00:27:48,400 --> 00:27:50,400
You're welcome, and good luck. Call if you need anything.

516
00:27:50,400 --> 00:27:52,400
Okay.

517
00:27:52,400 --> 00:27:54,400
So what's up?

518
00:27:54,400 --> 00:27:57,400
How will the treehouse detectives use pulleys to lift Jacob?

519
00:27:57,400 --> 00:27:59,400
Will it be safe?

520
00:27:59,400 --> 00:28:01,400
Is there a better solution?

521
00:28:01,400 --> 00:28:04,400
Stay tuned for the answers in the next exciting chapter of

522
00:28:04,400 --> 00:28:07,400
The Case of the Powerful Pulleys.

523
00:28:10,400 --> 00:28:13,400
Look for the answers to the following questions.

524
00:28:13,400 --> 00:28:17,400
How can we determine how much mass is needed to lift a treehouse detective?

525
00:28:17,400 --> 00:28:20,400
And how much mass is needed to lift a load?

526
00:28:21,400 --> 00:28:25,400
What should the treehouse detectives consider to safely lift Jacob?

527
00:28:26,400 --> 00:28:29,400
What are human factors?

528
00:28:31,400 --> 00:28:34,400
When you see this icon, the answer is near.

529
00:28:36,400 --> 00:28:39,400
And because pulleys reduce the amount of force needed.

530
00:28:39,400 --> 00:28:42,400
They're inexpensive, easy to set up, and operate.

531
00:28:42,400 --> 00:28:45,400
You must construct a pulley system.

532
00:28:45,400 --> 00:28:48,400
A pulley system is definitely the way to go.

533
00:28:50,400 --> 00:28:54,400
Okay, so we know we need to use pulleys to lift Jacob up into the treehouse.

534
00:28:54,400 --> 00:28:56,400
But how many do we need?

535
00:28:56,400 --> 00:28:59,400
I checked with the NASA Sci-Files Kids Club from Raleigh, North Carolina.

536
00:28:59,400 --> 00:29:02,400
I'll see if we can talk to them.

537
00:29:04,400 --> 00:29:07,400
Don't forget, we have to design the entire apparatus.

538
00:29:07,400 --> 00:29:11,400
I don't know about an apparatus, but a lift chair and a pulley system should be nice.

539
00:29:11,400 --> 00:29:13,400
Okay, fine.

540
00:29:13,400 --> 00:29:16,400
Seriously, we still need to design and build lift chairs.

541
00:29:16,400 --> 00:29:18,400
And the pulley system.

542
00:29:18,400 --> 00:29:21,400
Right, but we need to test both before we try and lift Jacob.

543
00:29:21,400 --> 00:29:24,400
Guys, the Sci-Files Kids Club. Check it out.

544
00:29:25,400 --> 00:29:31,400
Hi, I'm Katie. I'm Mrs. Nowell's fourth grade class at A.B. Compton Elementary School in Raleigh, North Carolina.

545
00:29:31,400 --> 00:29:33,400
Hi, how may I help you?

546
00:29:33,400 --> 00:29:38,400
Hi, we heard that you were working on an experiment to learn more about pulleys.

547
00:29:38,400 --> 00:29:41,400
That's right. We wanted to find out how pulleys work.

548
00:29:41,400 --> 00:29:43,400
Can you tell us about your experiment?

549
00:29:43,400 --> 00:29:53,400
Sure. First, each group was given 500 gram mass, two double pulleys, a cup, some string, and some pennies.

550
00:29:53,400 --> 00:29:58,400
We hooked the 500 gram mass to the bottom of the pulley system that we constructed.

551
00:29:58,400 --> 00:30:00,400
Their combined mass is called the load.

552
00:30:00,400 --> 00:30:02,400
What did you do with the pennies?

553
00:30:02,400 --> 00:30:06,400
We kept adding pennies to the cup until the load was lifted.

554
00:30:06,400 --> 00:30:11,400
We then placed our cup on a balance to find the total mass that it took to lift the load.

555
00:30:11,400 --> 00:30:17,400
Once we collected our data from two strings, we repeated with three and four strings.

556
00:30:17,400 --> 00:30:20,400
Did each group in the class get the same data?

557
00:30:20,400 --> 00:30:29,400
Not exactly. So we shared our data and took the class average of the total mass that it took to lift the load for each number of strings.

558
00:30:29,400 --> 00:30:33,400
When you analyzed your data, were you able to come to any conclusions?

559
00:30:33,400 --> 00:30:42,400
Yes. After putting the class averages up on the board, it was pretty obvious that the more strings we used, the less mass we needed to lift the load.

560
00:30:42,400 --> 00:30:46,400
How did you calculate how much mass you needed for each string?

561
00:30:46,400 --> 00:30:53,400
We counted the number of strings that supported the load and divided the combined mass by the string count.

562
00:30:53,400 --> 00:30:57,400
We saw right away that there was a problem when we did our first calculation.

563
00:30:57,400 --> 00:30:59,400
What was the problem?

564
00:30:59,400 --> 00:31:08,400
Our mass being lifted was 545 grams. When we had only one string, it should have taken 545 grams to lift it.

565
00:31:08,400 --> 00:31:12,400
Instead, it took an average of 571 grams.

566
00:31:12,400 --> 00:31:16,400
We also found the same thing in each of our other calculations.

567
00:31:16,400 --> 00:31:18,400
Could you have collected your data incorrectly?

568
00:31:18,400 --> 00:31:23,400
That's what we thought at first, or that we had made an error in our arithmetic.

569
00:31:23,400 --> 00:31:28,400
Our teacher gave us a hint. We realized that there was friction in our pulley system.

570
00:31:28,400 --> 00:31:33,400
Friction slows things down and makes it more difficult to lift.

571
00:31:33,400 --> 00:31:36,400
That's why you needed more mass to lift the load.

572
00:31:36,400 --> 00:31:47,400
Right. We concluded that you can find approximately how much mass is needed to lift the load by dividing by the number of strings, but you definitely have to consider friction.

573
00:31:47,400 --> 00:31:50,400
Thanks so much for your help. We won't forget about friction.

574
00:31:50,400 --> 00:31:53,400
You're welcome, and good luck on your project.

575
00:31:54,400 --> 00:31:59,400
I really like that experiment, but another way of looking at it is to say that the pulley multiplies in force.

576
00:31:59,400 --> 00:32:00,400
What?

577
00:32:00,400 --> 00:32:07,400
Look at it this way. If we have a load supported by four strings, the pulleys will allow us to lift something four times heavier than the force we apply.

578
00:32:07,400 --> 00:32:13,400
Oh, I get it. If I apply 10 pounds of force, then I can lift 40 pounds.

579
00:32:13,400 --> 00:32:14,400
Exactly.

580
00:32:14,400 --> 00:32:21,400
Mr. Jones said that we divide the total weight by the number of ropes supporting the load. The kids' club showed us how to do that, too.

581
00:32:21,400 --> 00:32:34,400
So if the total weight is 120 pounds, or 54 kilograms, and we had six ropes supporting the load, then that's about 20 pounds of pulling force, and with friction, maybe a little more.

582
00:32:34,400 --> 00:32:38,400
That would take about six pulleys.

583
00:32:40,400 --> 00:32:47,400
Wow. With my 20 pounds of force, I can lift 120 pounds. I've multiplied my force by six times.

584
00:32:47,400 --> 00:32:54,400
That's our new hypothesis. If we use rope, pulleys, and a lift chair, we can lift Jacob back into the treehouse.

585
00:32:54,400 --> 00:33:00,400
But what if I wanted to lift Jacob by myself? 20 pounds still seems like a lot to me.

586
00:33:00,400 --> 00:33:07,400
Maybe we can multiply our force even more by adding more rope and pulleys. It looks like we have some work to do.

587
00:33:18,400 --> 00:33:20,400
Okay, we're about ready to test.

588
00:33:20,400 --> 00:33:23,400
Wait, wait. We have a three-pulley system.

589
00:33:23,400 --> 00:33:27,400
I wish we'd found six pulleys. Do you think our hypothesis will still work?

590
00:33:27,400 --> 00:33:32,400
It should. With three pulleys, we'll need more force, but I think we can do it.

591
00:33:32,400 --> 00:33:35,400
And the test weight is 120 pounds.

592
00:33:35,400 --> 00:33:37,400
Okay, RJ, I think we're ready.

593
00:33:37,400 --> 00:33:39,400
Ready up here.

594
00:33:39,400 --> 00:33:41,400
Okay, we're ready to go.

595
00:33:41,400 --> 00:33:43,400
Ready up here.

596
00:33:43,400 --> 00:33:45,400
Okay, we're ready to go.

597
00:33:45,400 --> 00:33:52,400
According to my calculations, 120 pounds divided by three supporting ropes equals about 40 pounds of pulling force.

598
00:33:52,400 --> 00:33:54,400
Don't forget friction.

599
00:33:54,400 --> 00:33:57,400
Okay, 45. But we definitely need to pull together.

600
00:33:57,400 --> 00:34:02,400
Okay, everybody ready? One, two, three, pull.

601
00:34:12,400 --> 00:34:14,400
Where's Jacob?

602
00:34:16,400 --> 00:34:18,400
Oops.

603
00:34:18,400 --> 00:34:22,400
Treehouse, we have a problem. We need to do more research.

604
00:34:22,400 --> 00:34:24,400
We need to go to the problem board.

605
00:34:24,400 --> 00:34:26,400
Yeah.

606
00:34:27,400 --> 00:34:32,400
All right, we know that work is a force applied over a distance and that it takes energy to do work.

607
00:34:32,400 --> 00:34:35,400
We also know that a lever can change the direction of a force.

608
00:34:35,400 --> 00:34:38,400
And potential and kinetic energy can change back and forth.

609
00:34:38,400 --> 00:34:41,400
And pulleys reduce the amount of force needed to lift an object.

610
00:34:41,400 --> 00:34:44,400
First, we need to know how to make the lift chair safer.

611
00:34:44,400 --> 00:34:48,400
And we also need to know if there's anything else we can do to use less rope.

612
00:34:48,400 --> 00:34:50,400
Since we don't have any more pulleys,

613
00:34:50,400 --> 00:34:54,400
I think we need to find out if there's another simple machine that we can use to make it easier to lift Jacob.

614
00:34:54,400 --> 00:34:57,400
Until the test dummy fell off, it was difficult to pull.

615
00:34:57,400 --> 00:35:00,400
But now that we know how to do it, we can do it.

616
00:35:00,400 --> 00:35:02,400
We need to make it easier to lift Jacob.

617
00:35:02,400 --> 00:35:05,400
Until the test dummy fell off, it was difficult to pull.

618
00:35:05,400 --> 00:35:07,400
We need to talk to someone about safety.

619
00:35:07,400 --> 00:35:10,400
My mom works with some safety engineers at NASA Langley Research Center.

620
00:35:10,400 --> 00:35:13,400
I'll email her. Maybe she can help us.

621
00:35:14,400 --> 00:35:18,400
I'll go see Dr. D. Maybe he can help us figure out how to use less rope.

622
00:35:18,400 --> 00:35:22,400
We've still got some work to do before we let the real Jacob get anywhere near the treehouse.

623
00:35:22,400 --> 00:35:24,400
Great. My mom wrote back.

624
00:35:24,400 --> 00:35:28,400
Ms. Ryan is a safety engineer, and she's going to meet with us this afternoon.

625
00:35:28,400 --> 00:35:30,400
Great. Let's get up and go.

626
00:35:31,400 --> 00:35:34,400
Hi. We're the treehouse detectives. Are you Ms. Ryan?

627
00:35:34,400 --> 00:35:36,400
Yes. How can I help you today?

628
00:35:36,400 --> 00:35:38,400
We're designing a lift chair and a pulley system

629
00:35:38,400 --> 00:35:40,400
to help get our friend with a broken foot up into the treehouse.

630
00:35:40,400 --> 00:35:42,400
And we want to make sure that it is safe to use.

631
00:35:42,400 --> 00:35:44,400
Well, you've come to the right place.

632
00:35:44,400 --> 00:35:47,400
I am a safety engineer here at NASA Langley Research Center.

633
00:35:47,400 --> 00:35:49,400
What does a safety engineer do?

634
00:35:49,400 --> 00:35:51,400
Well, we do lots of things,

635
00:35:51,400 --> 00:35:55,400
like evaluating projects or jobs to identify potential hazards or risks.

636
00:35:55,400 --> 00:35:58,400
We also develop safety plans and guidelines

637
00:35:58,400 --> 00:36:01,400
that help prevent harmful accidents, incidents, or mishaps.

638
00:36:01,400 --> 00:36:05,400
Wow. That sounds like a cool job. And lots of responsibility.

639
00:36:05,400 --> 00:36:07,400
Yes. And we're doing more than developing rules.

640
00:36:07,400 --> 00:36:10,400
We're actually protecting people, property, and the environment.

641
00:36:10,400 --> 00:36:12,400
And we need to protect Jacob.

642
00:36:12,400 --> 00:36:14,400
What are some things that we should consider?

643
00:36:14,400 --> 00:36:16,400
How much will you be lifting?

644
00:36:16,400 --> 00:36:18,400
About 120 pounds.

645
00:36:18,400 --> 00:36:21,400
You'll need to know if there's a load limit on the ropes, pulleys, or anything else

646
00:36:21,400 --> 00:36:23,400
you will be using in the lifting process.

647
00:36:23,400 --> 00:36:25,400
We hadn't thought of that.

648
00:36:25,400 --> 00:36:27,400
How do you figure out the load limit?

649
00:36:27,400 --> 00:36:29,400
Most of the time it's printed on the packaging of a product.

650
00:36:29,400 --> 00:36:33,400
If not, look for the manufacturer and contact them directly.

651
00:36:33,400 --> 00:36:35,400
We will definitely do that.

652
00:36:35,400 --> 00:36:37,400
Is there a safety catch on your pulley system?

653
00:36:37,400 --> 00:36:39,400
No, I don't think so.

654
00:36:39,400 --> 00:36:42,400
A safety catch or a locking mechanism of some kind are very important

655
00:36:42,400 --> 00:36:45,400
in case the people pulling the rope lose their grip.

656
00:36:45,400 --> 00:36:47,400
It would catch and stop the fall of the chair.

657
00:36:47,400 --> 00:36:49,400
We have a lot to check out and to research.

658
00:36:49,400 --> 00:36:52,400
Also, make sure your equipment is in good working order.

659
00:36:52,400 --> 00:36:54,400
You don't want to use worn or broken equipment.

660
00:36:54,400 --> 00:36:57,400
And don't forget that we have to make sure the tree limb is strong enough

661
00:36:57,400 --> 00:37:00,400
to support Jacob, the lift chair, and the pulley system.

662
00:37:00,400 --> 00:37:02,400
Now you're getting it.

663
00:37:02,400 --> 00:37:05,400
And don't forget about testing your equipment before you lift anyone.

664
00:37:05,400 --> 00:37:07,400
We'll be sure to test everything.

665
00:37:07,400 --> 00:37:09,400
You'll also need to consider human factors.

666
00:37:09,400 --> 00:37:13,400
While you're here at the center, you should talk to Dr. Carla Torello.

667
00:37:13,400 --> 00:37:15,400
She's a human factors engineer.

668
00:37:15,400 --> 00:37:16,400
Great.

669
00:37:16,400 --> 00:37:18,400
I'll give her a call and let her know you're coming.

670
00:37:18,400 --> 00:37:19,400
Thanks.

671
00:37:19,400 --> 00:37:21,400
You're welcome, and good luck with your project.

672
00:37:23,400 --> 00:37:27,400
♪

673
00:37:27,400 --> 00:37:28,400
Oh, hi, Catherine.

674
00:37:28,400 --> 00:37:30,400
Laura Ryan said you'd be stopping by.

675
00:37:30,400 --> 00:37:33,400
Have a seat.

676
00:37:33,400 --> 00:37:34,400
How may I help you?

677
00:37:34,400 --> 00:37:36,400
Our friend Jacob broke his foot,

678
00:37:36,400 --> 00:37:39,400
and we've designed a lift chair to help him to get into the treehouse.

679
00:37:39,400 --> 00:37:42,400
Ms. Ryan gave us some good suggestions on how to make the chair safer,

680
00:37:42,400 --> 00:37:46,400
but she said that we should also consider the science of human factors.

681
00:37:46,400 --> 00:37:49,400
She said that you could help us with human factors.

682
00:37:49,400 --> 00:37:50,400
I sure can.

683
00:37:50,400 --> 00:37:53,400
Human factors is the design of things, spaces, and processes,

684
00:37:53,400 --> 00:37:57,400
so they fit better with people in terms of how people are designed physically

685
00:37:57,400 --> 00:37:59,400
and how we process information.

686
00:37:59,400 --> 00:38:00,400
Why is it important?

687
00:38:00,400 --> 00:38:03,400
Well, when things or processes or areas are designed

688
00:38:03,400 --> 00:38:05,400
without considering human factors,

689
00:38:05,400 --> 00:38:08,400
they may be really difficult to use, and so they may not be used at all.

690
00:38:08,400 --> 00:38:09,400
So where do you start?

691
00:38:09,400 --> 00:38:11,400
Well, we start with standards and guidelines

692
00:38:11,400 --> 00:38:13,400
that are based on scientific principles.

693
00:38:13,400 --> 00:38:16,400
And, for example, they help us understand how the eye works,

694
00:38:16,400 --> 00:38:19,400
which would help us understand what colors to use in our displays.

695
00:38:19,400 --> 00:38:20,400
Oh, I get it.

696
00:38:20,400 --> 00:38:22,400
Then we use what we know is good for human operators,

697
00:38:22,400 --> 00:38:25,400
and we get real operators involved in the process.

698
00:38:25,400 --> 00:38:26,400
This is called user-centered design.

699
00:38:26,400 --> 00:38:28,400
What are you working on now?

700
00:38:28,400 --> 00:38:30,400
Well, here at NASA Langley Research Center,

701
00:38:30,400 --> 00:38:33,400
we design displays and aiding technologies for airplane cockpits.

702
00:38:33,400 --> 00:38:37,400
We do user-centered design of these concepts by involving real pilots

703
00:38:37,400 --> 00:38:40,400
and testing them in aircraft simulators like this one, the IFD.

704
00:38:40,400 --> 00:38:41,400
What is the IFD?

705
00:38:41,400 --> 00:38:44,400
The IFD is integration flight deck.

706
00:38:44,400 --> 00:38:48,400
The IFD is a copy of the flight deck on the NASA Boeing 757.

707
00:38:48,400 --> 00:38:51,400
We learned that in designing, you have to use the iterative process,

708
00:38:51,400 --> 00:38:53,400
where you test, evaluate, and redesign.

709
00:38:53,400 --> 00:38:55,400
Human factors is sort of like that.

710
00:38:55,400 --> 00:38:56,400
Yes, that's right.

711
00:38:56,400 --> 00:39:00,400
The iterative design process is an important part of user-centered design.

712
00:39:00,400 --> 00:39:02,400
You want to involve users all the way through the process,

713
00:39:02,400 --> 00:39:06,400
from concept formation all the way through to testing in a real environment.

714
00:39:06,400 --> 00:39:09,400
What kind of human factors should we consider for our lift chair?

715
00:39:09,400 --> 00:39:11,400
Well, first you need to define your user population.

716
00:39:11,400 --> 00:39:13,400
Will Jacob be the only one using the chair?

717
00:39:13,400 --> 00:39:15,400
Will other friends use it as well?

718
00:39:15,400 --> 00:39:17,400
We hadn't thought of other users.

719
00:39:17,400 --> 00:39:20,400
It would be nice to have for other people who might need to be lifted.

720
00:39:20,400 --> 00:39:24,400
You need to consider your users' requirements, the design goals, too.

721
00:39:24,400 --> 00:39:27,400
So they may be safety, comfort, usability.

722
00:39:27,400 --> 00:39:28,400
Anything else?

723
00:39:28,400 --> 00:39:31,400
You need to consider the anthropometric characteristics of your users.

724
00:39:31,400 --> 00:39:34,400
Anthropometric? What is that?

725
00:39:34,400 --> 00:39:36,400
Anthropometry is the study of measuring people.

726
00:39:36,400 --> 00:39:39,400
There's static measurements, such as arm length and height,

727
00:39:39,400 --> 00:39:43,400
and then there's functional measurements, such as viewing angle and reach.

728
00:39:43,400 --> 00:39:45,400
Wow, we have a lot to consider.

729
00:39:45,400 --> 00:39:47,400
Thanks, Dr. Lattarella.

730
00:39:47,400 --> 00:39:50,400
Oh, you're welcome. Let me know how your chair works out.

731
00:39:52,400 --> 00:39:53,400
Hi, guys.

732
00:39:53,400 --> 00:39:54,400
Hi, Dr. D.

733
00:39:54,400 --> 00:39:55,400
What have you been doing?

734
00:39:55,400 --> 00:39:57,400
Just went for a bike ride to get a little exercise.

735
00:39:57,400 --> 00:39:58,400
How's your project coming?

736
00:39:58,400 --> 00:40:01,400
We're excited about using pulleys to lift Jacob into the treehouse.

737
00:40:01,400 --> 00:40:04,400
But we ended up with a lot of excess rope.

738
00:40:04,400 --> 00:40:06,400
Are we doing something wrong?

739
00:40:06,400 --> 00:40:08,400
I figured you'd have some questions about pulleys.

740
00:40:08,400 --> 00:40:11,400
So I set up a model over here. Let's try it out.

741
00:40:15,400 --> 00:40:19,400
I have 4 kilograms, or about 9 pounds, attached to this pulley system.

742
00:40:19,400 --> 00:40:21,400
Go ahead and pull on the string.

743
00:40:25,400 --> 00:40:26,400
That's really easy.

744
00:40:26,400 --> 00:40:29,400
Why don't you lift the weight, which we call the load 1 meter.

745
00:40:29,400 --> 00:40:31,400
We'll call this the load distance.

746
00:40:32,400 --> 00:40:33,400
Whoa!

747
00:40:45,400 --> 00:40:48,400
Wait a minute, Anthony. Where did all this string come from?

748
00:40:48,400 --> 00:40:51,400
I don't know. What's wrong?

749
00:40:51,400 --> 00:40:53,400
Nothing's wrong. Let me explain.

750
00:40:53,400 --> 00:40:56,400
Simple machines allow you to multiply your force.

751
00:40:56,400 --> 00:41:00,400
In this case, you can lift an object 8 times as heavy as your force.

752
00:41:00,400 --> 00:41:04,400
Right. We learned from the Sci-Files Kids Club that you count the number of strings supporting the load.

753
00:41:07,400 --> 00:41:10,400
I count 8 strings, and that's why we can multiply our force 8 times.

754
00:41:10,400 --> 00:41:12,400
Very good, but there is a trade-off.

755
00:41:12,400 --> 00:41:13,400
What do you mean?

756
00:41:13,400 --> 00:41:18,400
Remember that work is equal to force times distance.

757
00:41:18,400 --> 00:41:19,400
Okay.

758
00:41:19,400 --> 00:41:24,400
With simple machines like pulleys, you can multiply your force, but not the work.

759
00:41:24,400 --> 00:41:27,400
So in this case, you've multiplied your force 8 times.

760
00:41:27,400 --> 00:41:29,400
But how much string did you have to pull in?

761
00:41:32,400 --> 00:41:34,400
We'll call this your distance.

762
00:41:38,400 --> 00:41:42,400
8 meters. That means our distance is 8 times the load distance.

763
00:41:42,400 --> 00:41:44,400
Does it always work that way?

764
00:41:44,400 --> 00:41:45,400
Yes, it does.

765
00:41:45,400 --> 00:41:52,400
If you multiply your force, the trade-off is that your distance will always be greater than the load distance.

766
00:41:52,400 --> 00:41:54,400
Take a lever, for example.

767
00:41:58,400 --> 00:42:04,400
Why don't I stand over here, and have you try to lift me up by pushing over there.

768
00:42:04,400 --> 00:42:06,400
Try it with just one hand.

769
00:42:06,400 --> 00:42:07,400
Okay.

770
00:42:17,400 --> 00:42:19,400
I can't believe I just did that. That was easy.

771
00:42:19,400 --> 00:42:23,400
Well, if your force is 5 times further from the fulcrum, or over here,

772
00:42:23,400 --> 00:42:24,400
That was easy.

773
00:42:24,400 --> 00:42:29,400
Well, if your force is 5 times further from the fulcrum, or rotational point than the load,

774
00:42:29,400 --> 00:42:32,400
you will multiply your force by 5 times.

775
00:42:32,400 --> 00:42:39,400
But your distance, how far you push down, will also be 5 times greater than the load distance, how far I move up.

776
00:42:44,400 --> 00:42:46,400
This is really cool.

777
00:42:47,400 --> 00:42:53,400
So if simple machines don't allow us to do less work, or need less energy, why do we use them?

778
00:42:53,400 --> 00:42:55,400
I guess it's because they make the work easier.

779
00:42:55,400 --> 00:42:56,400
Excellent.

780
00:42:56,400 --> 00:42:58,400
We still need to make our work easier.

781
00:42:58,400 --> 00:43:01,400
Right now we've multiplied our force 3 times by using 3 pulleys,

782
00:43:01,400 --> 00:43:05,400
but that isn't enough to easily lift the load of 120 pounds.

783
00:43:05,400 --> 00:43:10,400
But if we add more pulleys to multiply the force even more, that means that we have to pull in a lot more rope.

784
00:43:10,400 --> 00:43:13,400
Wow. Maybe we need to use a different kind of simple machine.

785
00:43:13,400 --> 00:43:15,400
Well, don't scrap your pulley idea.

786
00:43:15,400 --> 00:43:19,400
You might want to consider combining other simple machines with your pulley system.

787
00:43:19,400 --> 00:43:21,400
You mean like use a lever with our pulley system?

788
00:43:21,400 --> 00:43:23,400
That's a possibility.

789
00:43:23,400 --> 00:43:25,400
Another one is a wheel and axle.

790
00:43:25,400 --> 00:43:27,400
Take my bike, for example.

791
00:43:29,400 --> 00:43:31,400
This could also be called a crank and axle.

792
00:43:31,400 --> 00:43:34,400
This wheel with the chain attached is the axle.

793
00:43:34,400 --> 00:43:37,400
It's attached to this crank with the pedal.

794
00:43:37,400 --> 00:43:39,400
To find out how this machine multiplies the force,

795
00:43:39,400 --> 00:43:44,400
all we have to do is divide the radius of the crank by the radius of the axle.

796
00:43:44,400 --> 00:43:46,400
RJ, would you make the measurements, please?

797
00:43:55,400 --> 00:43:59,400
The crank is 16 centimeters and the axle is 8 centimeters,

798
00:43:59,400 --> 00:44:02,400
so that means the machine multiplies the force by 2.

799
00:44:02,400 --> 00:44:04,400
That's great.

800
00:44:05,400 --> 00:44:08,400
Another possibility you may want to explore is gears.

801
00:44:08,400 --> 00:44:10,400
I'm going to visit my grandparents in San Diego.

802
00:44:10,400 --> 00:44:12,400
We're planning on going to Legoland.

803
00:44:12,400 --> 00:44:14,400
I bet there are a lot of gears in Legoland.

804
00:44:14,400 --> 00:44:17,400
I'll send them an email and see if I can speak with someone about gears.

805
00:44:17,400 --> 00:44:18,400
Great.

806
00:44:18,400 --> 00:44:19,400
Bye, Dr. D.

807
00:44:19,400 --> 00:44:20,400
Thanks.

808
00:44:20,400 --> 00:44:21,400
Bye.

809
00:44:22,400 --> 00:44:23,400
So what's up?

810
00:44:23,400 --> 00:44:26,400
Will the Treehouse Detectives be able to make the lift chair safe?

811
00:44:26,400 --> 00:44:29,400
How will human factors change the design of the lift chair?

812
00:44:29,400 --> 00:44:33,400
What other simple machines can the Treehouse Detectives use to help them lift Jacob?

813
00:44:33,400 --> 00:44:37,400
Find out in the conclusion of The Case of the Powerful Pulleys.

814
00:44:39,400 --> 00:44:44,400
Answer these final questions and help solve The Case of the Powerful Pulleys.

815
00:44:44,400 --> 00:44:46,400
How does a gear work?

816
00:44:47,400 --> 00:44:50,400
How does a belay make the lift chair safer?

817
00:44:51,400 --> 00:44:54,400
How does a winch help solve the problem?

818
00:44:55,400 --> 00:44:58,400
Can you see this icon? The answer is near.

819
00:45:08,400 --> 00:45:13,400
The Case of the Powerful Pulleys

820
00:45:26,400 --> 00:45:27,400
Hello, Mrs. Savelle.

821
00:45:27,400 --> 00:45:30,400
Hi. You must be one of the Treehouse Detectives.

822
00:45:30,400 --> 00:45:32,400
I understand you need to learn about gears.

823
00:45:32,400 --> 00:45:35,400
We sure do. What exactly is a gear?

824
00:45:35,400 --> 00:45:39,400
A gear is one of the oldest simple machines invented.

825
00:45:39,400 --> 00:45:43,400
In fact, it's a wheel and an axle but with teeth.

826
00:45:43,400 --> 00:45:45,400
Teeth? What kind of teeth?

827
00:45:45,400 --> 00:45:48,400
I'll use these Lego gears to show you.

828
00:45:48,400 --> 00:45:49,400
That's cool.

829
00:45:49,400 --> 00:45:55,400
Gears work when the teeth of one gear mesh with the teeth of another.

830
00:45:58,400 --> 00:46:02,400
The first gear is called the driver or the primary gear.

831
00:46:02,400 --> 00:46:12,400
Notice when I turn it, the next gear or the follower gear rotates in the opposite direction but at the same rotational speed.

832
00:46:12,400 --> 00:46:15,400
What happens when you put two gears together that aren't the same size?

833
00:46:15,400 --> 00:46:23,400
Let's see. Notice that the follower gear is two times larger and has twice as many teeth as the driving gear.

834
00:46:23,400 --> 00:46:24,400
Give it a try.

835
00:46:28,400 --> 00:46:31,400
The follower only rotates half as much as the driver.

836
00:46:31,400 --> 00:46:35,400
That's right. It has half the rotational speed of the driver.

837
00:46:35,400 --> 00:46:39,400
Changing rotational speed is one of the reasons we use gears.

838
00:46:39,400 --> 00:46:46,400
Another reason is to multiply the force on the axle of the follower gear.

839
00:46:46,400 --> 00:46:50,400
We definitely need more force but how do you use gears to multiply force?

840
00:46:50,400 --> 00:46:57,400
It's simple. If you double the size of the follower gear, the force on the axle is twice what it used to be.

841
00:46:57,400 --> 00:46:59,400
Is it always that easy?

842
00:46:59,400 --> 00:47:08,400
You can actually calculate the increase in force by simply dividing the number of teeth on the follower with the number of teeth on the driver.

843
00:47:08,400 --> 00:47:12,400
So in this case, the follower has 40 teeth and the driver has 24.

844
00:47:12,400 --> 00:47:19,400
40 divided by 24 is about 1.7. That means that the force is multiplied about two times.

845
00:47:19,400 --> 00:47:22,400
That's right. You're really good with numbers.

846
00:47:22,400 --> 00:47:24,400
What if there are three gears?

847
00:47:24,400 --> 00:47:25,400
Let's try it.

848
00:47:26,400 --> 00:47:34,400
Here we have a driver with 8 teeth, a follower with 24 teeth, and another follower with 40 teeth.

849
00:47:38,400 --> 00:47:43,400
It looks like the driver gear goes around five times for every one time that the largest follower gear goes around.

850
00:47:43,400 --> 00:47:52,400
Good observation. To find the force multiplier, you divide the 40 teeth of the follower by the 8 teeth of the driver.

851
00:47:52,400 --> 00:47:55,400
That would be five. But what about the middle gear?

852
00:47:55,400 --> 00:48:00,400
The middle gear doesn't make a difference except for the fact that it changes the direction of rotation.

853
00:48:00,400 --> 00:48:05,400
Let's verify our results to see if the force is really multiplied by five.

854
00:48:05,400 --> 00:48:14,400
I'll place five bricks on this lever arm and place one brick the same distance out on the lever arm on the driver gear.

855
00:48:14,400 --> 00:48:16,400
It balances, so we were correct.

856
00:48:16,400 --> 00:48:20,400
We've multiplied the force by five, but the follower doesn't move very much at all.

857
00:48:20,400 --> 00:48:22,400
It's just like a pulley system.

858
00:48:22,400 --> 00:48:26,400
Whenever you multiply the force, you have to pull in a lot of rope to move the load a short distance.

859
00:48:26,400 --> 00:48:30,400
Right. Whenever you use simple machines, there's always a tradeoff.

860
00:48:30,400 --> 00:48:32,400
Dr. D. said the same thing.

861
00:48:32,400 --> 00:48:37,400
He also said that you could combine simple machines in order to get a greater multiplication of force.

862
00:48:37,400 --> 00:48:40,400
Check out this bicycle, for example.

863
00:48:40,400 --> 00:48:42,400
The crank works as a lever.

864
00:48:42,400 --> 00:48:44,400
We have a gear system.

865
00:48:44,400 --> 00:48:48,400
In this gear system, the teeth don't mesh together directly.

866
00:48:48,400 --> 00:48:51,400
They are connected by a chain.

867
00:48:51,400 --> 00:48:53,400
A bicycle uses a lot of simple machines.

868
00:48:53,400 --> 00:49:01,400
When you have more than one simple machine working together, like on the bicycle, it's called a compound machine.

869
00:49:01,400 --> 00:49:03,400
Here's another example.

870
00:49:03,400 --> 00:49:13,400
This crane is a combination of a crank or lever attached to a gear connected to pulleys.

871
00:49:13,400 --> 00:49:17,400
This is really cool. I'll bet that this helps us solve our problem.

872
00:49:17,400 --> 00:49:18,400
Thanks a lot, Ms. Salvell.

873
00:49:18,400 --> 00:49:20,400
You're welcome.

874
00:49:24,400 --> 00:49:26,400
I think this is our new hypothesis.

875
00:49:26,400 --> 00:49:32,400
If we use rope, pulleys, gears, and a lift chair, then we'll be able to lift Jacob into the treehouse.

876
00:49:34,400 --> 00:49:39,400
Okay, we can secure Jacob or anyone else in the lift chair by using this rope and harness.

877
00:49:39,400 --> 00:49:41,400
Yes, and the handles make it safer, too.

878
00:49:41,400 --> 00:49:45,400
As long as the lift chair can support the heaviest passenger, then we're in good shape.

879
00:49:45,400 --> 00:49:49,400
Right. Now all we have to figure out is how to make the pulley system easy enough for everyone to use.

880
00:49:49,400 --> 00:49:51,400
Let's go and see if Anthony sent us an email.

881
00:49:54,400 --> 00:49:59,400
Anthony said that he learned a lot at Legoland about gears and combining simple machines together.

882
00:49:59,400 --> 00:50:02,400
He said that he remembers seeing a lot of things in his garage.

883
00:50:02,400 --> 00:50:05,400
He thinks it might be a good idea to use gears with our pulley system.

884
00:50:05,400 --> 00:50:07,400
He wants us to check with his dad about using it.

885
00:50:07,400 --> 00:50:09,400
I wonder what has gears in it.

886
00:50:09,400 --> 00:50:11,400
We'll have to check this out.

887
00:50:11,400 --> 00:50:13,400
Oh, Dr. D wrote us an email.

888
00:50:13,400 --> 00:50:16,400
He said that if we're concerned about safety, we should talk to his climber friends.

889
00:50:16,400 --> 00:50:20,400
Great. While you're on the Internet, print out a get-up-and-go sheet.

890
00:50:20,400 --> 00:50:25,400
You can print out your own get-up-and-go sheet by going to the NASA SciFiles website research track.

891
00:50:29,400 --> 00:50:31,400
Hi. Are you Mr. Harding?

892
00:50:31,400 --> 00:50:34,400
Yes, that's right. You must be one of the treehouse detectives.

893
00:50:34,400 --> 00:50:37,400
Dr. D tells me you need to learn more about safety.

894
00:50:37,400 --> 00:50:40,400
That's right. Dr. D mentioned that you rock climb.

895
00:50:40,400 --> 00:50:42,400
We were wondering how you make it safe.

896
00:50:42,400 --> 00:50:47,400
I can show you that right here, but first we need to outfit you with the climbing harness to tie the rope into you.

897
00:50:48,400 --> 00:50:50,400
You aren't going to pull me up, are you?

898
00:50:50,400 --> 00:50:55,400
No, you're going to have to do the climbing yourself. The rope is just simply there to keep you safe.

899
00:50:55,400 --> 00:50:56,400
How does that work?

900
00:50:56,400 --> 00:50:57,400
It's called belaying.

901
00:50:57,400 --> 00:51:05,400
I tie one end of the rope into your harness, and then it goes through the eye bolt at the top, and then down to me, the belayer.

902
00:51:05,400 --> 00:51:09,400
It passes through this belay device called an ATC or figure eight.

903
00:51:09,400 --> 00:51:15,400
If you slip and begin to fall, I simply pull on the rope like this, and the friction with the ATC stops the rope.

904
00:51:15,400 --> 00:51:17,400
Are you sure this is going to work?

905
00:51:17,400 --> 00:51:18,400
Let me show you.

906
00:51:19,400 --> 00:51:21,400
Climb up a few feet and then let go.

907
00:51:27,400 --> 00:51:28,400
Okay.

908
00:51:33,400 --> 00:51:35,400
Wow. It stopped me right away.

909
00:51:35,400 --> 00:51:36,400
I told you it would.

910
00:51:36,400 --> 00:51:39,400
Another important safety feature is the type of rope we're using.

911
00:51:39,400 --> 00:51:42,400
It's called a dynamic rope because it has stretch to it.

912
00:51:42,400 --> 00:51:44,400
That way you don't stop too suddenly.

913
00:51:47,400 --> 00:51:49,400
You want to try some rappelling?

914
00:51:49,400 --> 00:51:50,400
What's that?

915
00:51:50,400 --> 00:51:52,400
Let me have my son demonstrate.

916
00:51:53,400 --> 00:51:54,400
Okay.

917
00:52:04,400 --> 00:52:07,400
It looks like he used the same device that you used to belay me.

918
00:52:07,400 --> 00:52:10,400
That's right. I have a belay attached to him to keep him safe.

919
00:52:10,400 --> 00:52:14,400
I'll bet we could use the belay principle as a safety device for a lift chair.

920
00:52:23,400 --> 00:52:25,400
Boy, Jacob sure is heavy.

921
00:52:26,400 --> 00:52:28,400
Simple machines sure help.

922
00:52:28,400 --> 00:52:30,400
I'm glad we don't have to live all this way to look.

923
00:52:30,400 --> 00:52:32,400
Hey, here comes Dr. D.

924
00:52:33,400 --> 00:52:35,400
I'll take off the dummy while you can lower the chair.

925
00:52:35,400 --> 00:52:36,400
Okay.

926
00:52:52,400 --> 00:52:55,400
This looks impressive. How did you put it all together?

927
00:52:55,400 --> 00:52:59,400
Well, the obvious answer was pulleys, but that was just the beginning.

928
00:52:59,400 --> 00:53:03,400
We could only find three pulleys, so the best that we could do was multiply the force three times.

929
00:53:03,400 --> 00:53:05,400
Jacob is way too heavy for that.

930
00:53:05,400 --> 00:53:07,400
Hey, I'm not that heavy.

931
00:53:08,400 --> 00:53:13,400
But we learned that we could combine simple machines, like gears, with the pulleys to multiply the force even more.

932
00:53:13,400 --> 00:53:15,400
There was also a safety concern.

933
00:53:15,400 --> 00:53:19,400
We learned how to use the rock climbing technique of belaying to help keep Jacob safe.

934
00:53:19,400 --> 00:53:23,400
And the winch we found not only had gears, but also a wheel and axle to help make the work easier.

935
00:53:23,400 --> 00:53:25,400
It also had a built-in safety device.

936
00:53:25,400 --> 00:53:27,400
I think it's called a ratchet.

937
00:53:27,400 --> 00:53:28,400
Yes, it is.

938
00:53:28,400 --> 00:53:33,400
A ratchet keeps the handle from spinning wildly or turning backwards if you accidentally let go.

939
00:53:33,400 --> 00:53:36,400
We also learned that simple machines don't reduce the energy needed.

940
00:53:36,400 --> 00:53:38,400
They just make work easier.

941
00:53:38,400 --> 00:53:43,400
Instead of using a very big force for the distance of 3.5 meters up into the treehouse,

942
00:53:43,400 --> 00:53:45,400
we can use a very small force on the crank.

943
00:53:45,400 --> 00:53:48,400
That means that we'll have to turn the crank a lot of times.

944
00:53:48,400 --> 00:53:52,400
Right, and we can all use the system by ourselves to lift up any one of us.

945
00:53:52,400 --> 00:53:56,400
Right, we know the force needed is small, but do we ever figure it out exactly?

946
00:53:56,400 --> 00:53:57,400
No.

947
00:53:57,400 --> 00:53:59,400
Dr. D., can you help us with that?

948
00:53:59,400 --> 00:54:00,400
Sure.

949
00:54:00,400 --> 00:54:02,400
How much do the pulleys multiply the force?

950
00:54:02,400 --> 00:54:06,400
The load is supported by three ropes, so the force is multiplied three times.

951
00:54:06,400 --> 00:54:07,400
Good.

952
00:54:07,400 --> 00:54:09,400
How about the gears on your winch?

953
00:54:09,400 --> 00:54:13,400
We learned at Legoland that we need to count the number of teeth on both gears.

954
00:54:13,400 --> 00:54:17,400
The big gear on our winch has 41 teeth, and the little gear has 10 teeth.

955
00:54:17,400 --> 00:54:20,400
So the gears alone multiply our force about four times.

956
00:54:20,400 --> 00:54:22,400
We've learned a lot about simple machines.

957
00:54:22,400 --> 00:54:24,400
There's also a crank on the winch.

958
00:54:24,400 --> 00:54:27,400
It's got a radius about five times longer than the spool.

959
00:54:27,400 --> 00:54:29,400
That multiplies the force five times.

960
00:54:29,400 --> 00:54:31,400
Right, just like the bicycle crank.

961
00:54:31,400 --> 00:54:33,400
The spool also gathers the excess rope.

962
00:54:33,400 --> 00:54:36,400
And because we use gears and a wheel and axle along with our pulleys,

963
00:54:36,400 --> 00:54:38,400
we didn't have to pull in as much rope.

964
00:54:38,400 --> 00:54:41,400
We multiplied the force three times for the pulleys, four times for the gears,

965
00:54:41,400 --> 00:54:43,400
and five times for the wheel and axle.

966
00:54:43,400 --> 00:54:45,400
But how do those go together?

967
00:54:45,400 --> 00:54:48,400
All you have to do is multiply the three numbers together.

968
00:54:48,400 --> 00:54:50,400
That's easy. Let's see.

969
00:54:50,400 --> 00:54:54,400
Three times four is 12, and 12 times five is 60.

970
00:54:54,400 --> 00:54:57,400
So our compound machine multiplies our force 60 times.

971
00:54:57,400 --> 00:55:00,400
Since two times 60 is equal to 120,

972
00:55:00,400 --> 00:55:05,400
that means that we'll only need about two pounds of force to lift 120 pounds.

973
00:55:05,400 --> 00:55:08,400
So is it true that your force will actually be multiplied 60 times?

974
00:55:08,400 --> 00:55:10,400
Isn't that what the math says?

975
00:55:10,400 --> 00:55:12,400
You can always trust math.

976
00:55:12,400 --> 00:55:15,400
Wait a minute. When we were measuring the force on our spring scale,

977
00:55:15,400 --> 00:55:19,400
when we were testing the pulley system, it read five pounds, not two.

978
00:55:19,400 --> 00:55:20,400
I don't get it.

979
00:55:20,400 --> 00:55:22,400
Well, don't forget what you learned from the Sci-Files Kids Club.

980
00:55:22,400 --> 00:55:24,400
Yes, there's always some friction.

981
00:55:24,400 --> 00:55:26,400
Don't forget about the tradeoff.

982
00:55:26,400 --> 00:55:29,400
Right. If our force is multiplied by 60 times,

983
00:55:29,400 --> 00:55:31,400
then the distance will be 60 times more.

984
00:55:31,400 --> 00:55:35,400
Wow, 60 times 3.5 meters up to the treehouse.

985
00:55:35,400 --> 00:55:37,400
That's about 210 meters.

986
00:55:37,400 --> 00:55:39,400
That's a lot of cranking.

987
00:55:39,400 --> 00:55:42,400
Yes, but it's certainly easier than just pulling him in.

988
00:55:42,400 --> 00:55:43,400
And it's safer, too.

989
00:55:43,400 --> 00:55:45,400
Yeah, but it takes a lot longer.

990
00:55:45,400 --> 00:55:47,400
Let's try it out. We have tested it.

991
00:55:47,400 --> 00:55:50,400
We know it'll be easy and safe. Let's do it.

992
00:55:50,400 --> 00:55:51,400
Let's not move too fast.

993
00:55:51,400 --> 00:55:54,400
Remember, I already have one broken foot.

994
00:55:54,400 --> 00:55:55,400
I don't want another.

995
00:55:55,400 --> 00:55:57,400
Don't worry. We'll take good care of you.

996
00:56:10,400 --> 00:56:12,400
Let us know when you're ready.

997
00:56:12,400 --> 00:56:14,400
Okay. I'm ready down here.

998
00:56:39,400 --> 00:56:41,400
Wow, you guys did it.

999
00:56:41,400 --> 00:56:43,400
I can't believe I'm back in the treehouse.

1000
00:56:43,400 --> 00:56:45,400
Simple machines are simply amazing.

1001
00:56:45,400 --> 00:56:47,400
Good work, everyone.

1002
00:56:55,400 --> 00:56:57,400
It worked perfectly, Dr. D.

1003
00:56:57,400 --> 00:56:58,400
Thanks for your help.

1004
00:56:58,400 --> 00:57:00,400
You're welcome, kids.

1005
00:57:00,400 --> 00:57:02,400
You left the excellent work. See ya.

1006
00:57:02,400 --> 00:57:03,400
Bye, Dr. D.

1007
00:57:04,400 --> 00:57:06,400
Another successful project.

1008
00:57:06,400 --> 00:57:08,400
And this time you guys didn't need my help.

1009
00:57:10,400 --> 00:57:12,400
I am ToonBot 3000.

1010
00:57:12,400 --> 00:57:15,400
Welcome to the news, news, news.

1011
00:57:15,400 --> 00:57:18,400
Top Story, Career Day.

1012
00:57:18,400 --> 00:57:22,400
We go live to I Am List, List, Listening.

1013
00:57:22,400 --> 00:57:25,400
Thanks, uh, ToonBot.

1014
00:57:25,400 --> 00:57:30,400
Well, folks, I discovered that I am no expert on renovations or construction.

1015
00:57:30,400 --> 00:57:33,400
And I will not be changing careers.

1016
00:57:33,400 --> 00:57:38,400
If you want to talk to some real experts and learn about some great career fields,

1017
00:57:38,400 --> 00:57:40,400
come down to Career Day tomorrow.

1018
00:57:40,400 --> 00:57:43,400
Back to you, ToonBot.

1019
00:57:43,400 --> 00:57:47,400
Bang, bang, bang, bang, bang, bang, bang, bang.

1020
00:57:48,400 --> 00:57:52,400
Hi, folks. One last little renovation to take care of.

1021
00:57:53,400 --> 00:57:56,400
I'm Ted Toon with KSNN.

1022
00:57:56,400 --> 00:57:59,400
That's right. You're doing a presentation tomorrow. How's it coming?

1023
00:57:59,400 --> 00:58:03,400
Well, thanks to the treehouse detectives, NASA engineers, and SWE,

1024
00:58:03,400 --> 00:58:05,400
I think it's going to turn out great.

1025
00:58:05,400 --> 00:58:09,400
This pulley system and lift chair makes you a first-class treehouse engineer.

1026
00:58:09,400 --> 00:58:11,400
We're all engineers.

1027
00:58:11,400 --> 00:58:13,400
You guys are the best. One question, though.

1028
00:58:13,400 --> 00:58:16,400
Does this pulley system work as well going down?

1029
00:58:16,400 --> 00:58:20,400
Uh-oh. We didn't think about getting you back down.

1030
00:58:20,400 --> 00:58:22,400
Dr. D!

1031
00:58:27,400 --> 00:58:29,400
Guys?

1032
00:58:29,400 --> 00:58:31,400
Guys?

1033
00:58:31,400 --> 00:58:33,400
Guys?

1034
00:58:33,400 --> 00:58:35,400
Guys?

1035
00:58:35,400 --> 00:58:37,400
Guys?

1036
00:58:46,400 --> 00:58:50,400
The NASA Science Files is made possible through the generous support of

1037
00:58:50,400 --> 00:58:53,400
Busch Gardens, SeaWorld, and NASA Langley Research Center's

1038
00:58:53,400 --> 00:58:56,400
Aerospace Vehicle System Technology Office.

1039
00:58:56,400 --> 00:59:00,400
Captioning provided by NEC Foundation of America.