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Crash Test Pulleys

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Subido el 28 de mayo de 2007 por EducaMadrid

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NASA Sci Files segment explaining how pulleys make lifiting easier, and how NASA uses pulleys to conduct crash tests for aircraft.

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Hi RJ, Bianca's mom said you'd be coming by, how can I help you? 00:00:00
We need to learn more about pulleys. What exactly is a pulley? 00:00:03
Well, a pulley is a simple machine. It's made from a rope and a wheel. 00:00:06
It makes lifting objects easier. 00:00:11
How does it do that? 00:00:13
It changes the direction of the force. 00:00:14
For example, if you're lifting a heavy object off the floor, 00:00:16
using a pulley mounted to the ceiling, 00:00:20
you can pull down the rope instead of pushing up. 00:00:22
Aren't you using the same amount of force needed to lift an object? 00:00:25
Good question. Yes you are, but it's easier to pull down than to push up. 00:00:28
So how would I reduce the amount of force needed to lift a heavy object? 00:00:32
If you add a second pulley and you support the load with two ropes, 00:00:39
then you only need half of the force to lift it. 00:00:42
What if you add a third pulley and support the load with three ropes? 00:00:45
If you divide the weight of the object by the number of ropes supporting the load, 00:00:49
then you can determine what kind of force you need to lift the object. 00:00:53
Awesome. So what do you use pulleys for here at NASA Langer Research Center? 00:00:56
As an aerospace engineer and a Level 3 manager of NASA's Aviation Safety Program, 00:01:00
I use pulleys in crashworthiness research. 00:01:05
What's crashworthiness? 00:01:08
Crashworthiness is how well an aircraft protects occupants in a crash. 00:01:10
A team of engineers and I conduct tests and analysis on materials, 00:01:14
on aircraft structures and full-scale aircraft. 00:01:18
Why is that important? 00:01:20
In a real crash, it is very difficult to understand the damage 00:01:22
because many things are destroyed. 00:01:25
By conducting controlled crash tests, we can better understand what happens in a real crash, 00:01:27
and then we can develop better designs that will protect the passengers. 00:01:31
You crash real airplanes here? 00:01:36
We sure do, right here at the gantry. 00:01:38
What exactly is the gantry? 00:01:40
The gantry is the Impact Dynamics Research Facility where we perform full-scale crash tests. 00:01:42
It was also used by astronauts during the Apollo missions to practice landing on the moon. 00:01:46
That's cool. How do you crash planes? 00:01:50
A test vehicle is suspended from two swing cables, 00:01:53
pulled back and released to allow the test vehicle to swing into the impact surface below. 00:01:56
The swing cables are pyrotechnically separated from the vehicle just prior to the impact 00:02:00
so that free flight conditions are established. 00:02:04
Airplanes are really heavy. You must need a lot of pulleys. 00:02:07
Actually, we only use one pulley, but it's a pretty big pulley. 00:02:10
How much can you lift? 00:02:13
We currently can only lift up to 30,000 pounds 00:02:15
because that's the maximum capacity of the gantry's bridge. 00:02:17
How can you lift 30,000 pounds? 00:02:20
I run steel rope from the lifting device through the pulley and then attach it back to the bridge. 00:02:22
The pulley is attached to the aircraft. This is called double hitching. 00:02:27
30,000 pounds is a lot of weight. 00:02:30
Yes, it is, but we don't need 30,000 pounds of force to lift it. 00:02:32
With one pulley attached to the aircraft, you have two ropes supporting the load. 00:02:35
Then you only need 15,000 pounds of force. 00:02:39
Alfred and Jacob doesn't weigh 30,000 pounds, 00:02:42
so I bet we could use pulleys to lift them with no problem at all. 00:02:45
Thanks, Mrs. Jones. 00:02:48
You're welcome and good luck. Call if you need anything. 00:02:49
Okay. 00:02:51
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Idioma/s:
en
Niveles educativos:
▼ Mostrar / ocultar niveles
      • Nivel Intermedio
Autor/es:
NASA LaRC Office of Education
Subido por:
EducaMadrid
Licencia:
Reconocimiento - No comercial - Sin obra derivada
Visualizaciones:
680
Fecha:
28 de mayo de 2007 - 15:32
Visibilidad:
Público
Enlace Relacionado:
NASAs center for distance learning
Duración:
02′ 52″
Relación de aspecto:
4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
Resolución:
480x360 píxeles
Tamaño:
17.42 MBytes

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