1 00:00:00,000 --> 00:00:04,000 Now it's your turn to try the online activity found at the NASA Connect website. 2 00:00:04,000 --> 00:00:10,000 Your challenge is to get the PSA to the overheated racks before the time runs out. 3 00:00:10,000 --> 00:00:16,000 Each click gives the PSA one unit of force in the direction of the arrows. 4 00:00:16,000 --> 00:00:24,000 Remember Newton's Law. The PSA will keep moving unless you apply another force to it in the opposite direction. 5 00:00:24,000 --> 00:00:30,000 Your teacher will now pause the program so that you can go to your computers and check out the activity. 6 00:00:30,000 --> 00:00:35,000 I gave the PSA too much force. It hit the side of the ISS. 7 00:00:35,000 --> 00:00:39,000 The PSA keeps moving after you have applied a force to it. 8 00:00:39,000 --> 00:00:44,000 You have to apply a force in the opposite direction to stop the PSA. 9 00:00:44,000 --> 00:00:48,000 Newton also had something to say about motion and the mass of objects. 10 00:00:48,000 --> 00:00:52,000 The more massive an object is, the more force is required to accelerate it or to stop it. 11 00:00:53,000 --> 00:01:01,000 So if the PSA is very massive, for instance, it's going to take a lot of force to get it moving and a lot of force to stop it. 12 00:01:01,000 --> 00:01:05,000 You're right. The greater the mass of the PSA, the more force it takes to slow it down. 13 00:01:05,000 --> 00:01:11,000 The fans have to work harder. If we make the PSA lighter, it requires less force to slow it down and to stop it. 14 00:01:11,000 --> 00:01:16,000 If the PSA was going to go too fast, it might bump into the side of the ISS. 15 00:01:16,000 --> 00:01:19,000 So we need to make the PSA as light as possible. 16 00:01:19,000 --> 00:01:23,000 The model that you see here is the 12-inch working prototype. 17 00:01:23,000 --> 00:01:28,000 Our goal is to reduce the PSA size down to this 8-inch diameter model. 18 00:01:28,000 --> 00:01:33,000 With the invention of the transistor, computers and other electronic gadgets became smaller and smaller. 19 00:01:33,000 --> 00:01:40,000 That's right. You know, when our grandparents were kids, they listened to radios that were like large pieces of furniture. 20 00:01:40,000 --> 00:01:43,000 Today, radios and digital players are really tiny. 21 00:01:43,000 --> 00:01:47,000 That's right. A computer with the same power as this PDA filled this huge room. 22 00:01:47,000 --> 00:01:49,000 The PSA has a computer inside it. 23 00:01:49,000 --> 00:01:57,000 And in addition, the PSA can connect to computers on the space station or on Earth with a wireless connection and use the computing power of those computers. 24 00:01:57,000 --> 00:02:02,000 So the PSA can be small because it doesn't need a big computer inside of it. 25 00:02:02,000 --> 00:02:06,000 But why is it round? And how do you make the shell round? 26 00:02:06,000 --> 00:02:11,000 Round shapes don't have any sharp corners, so the PSA won't accidentally damage the ISS. 27 00:02:11,000 --> 00:02:15,000 We designed the round shell with a computer program for solid modeling. 28 00:02:15,000 --> 00:02:20,000 Once the design is complete, we send an electronic file to the manufacturer to create a shell. 29 00:02:20,000 --> 00:02:24,000 The process is called stereolithography, or SLA. 30 00:02:24,000 --> 00:02:31,000 To make the PSA smaller, we need to redesign and shrink the parts in the PSA so that they fit into a smaller sphere. 31 00:02:31,000 --> 00:02:35,000 Wait a minute. I don't know if that's the best way to do it. 32 00:02:35,000 --> 00:02:38,000 When we make things smaller, though, we have to keep some things in mind. 33 00:02:38,000 --> 00:02:43,000 For example, the computer that's in the PSA needs to have space around it so that it can stay cool. 34 00:02:43,000 --> 00:02:48,000 The computer gives off its heat from the surface area of the board, which means we need to provide space for cooling. 35 00:02:48,000 --> 00:02:52,000 Additionally, when we consider shrinking the fans to fit in a smaller PSA, 36 00:02:52,000 --> 00:02:56,000 we discover they became very inefficient, forcing us to move to a blower design. 37 00:02:56,000 --> 00:02:59,000 It's similar to how a leaf blower works. 38 00:02:59,000 --> 00:03:05,000 Okay, guys, let's review some math concepts so you can figure out how to fit your parts into the PSA. 39 00:03:05,000 --> 00:03:11,000 This is a rectangular prism. Now, each one of its six sides is a rectangle. 40 00:03:11,000 --> 00:03:17,000 The surface area of the rectangular prism is the sum of the areas of the six sides. 41 00:03:17,000 --> 00:03:23,000 The volume of a rectangular prism is the area of the base times the height of the prism. 42 00:03:23,000 --> 00:03:26,000 Let's take a look at cylinders. 43 00:03:26,000 --> 00:03:29,000 The base of a cylinder is a circle. 44 00:03:29,000 --> 00:03:32,000 Let's take a look at the parts of a circle. 45 00:03:32,000 --> 00:03:36,000 The circumference is the distance around a circle. 46 00:03:36,000 --> 00:03:41,000 The radius is the distance from the center of a circle to any point on the circle. 47 00:03:41,000 --> 00:03:45,000 The diameter of a circle is twice the radius. 48 00:03:45,000 --> 00:03:53,000 Thousands of years ago, mathematicians measured the circumference of circles and divided the circumference by the diameter. 49 00:03:53,000 --> 00:03:57,000 They always came up with the same number, around 3.14. 50 00:03:57,000 --> 00:04:00,000 This number is called pi. 51 00:04:00,000 --> 00:04:05,000 Now, watch this and see how we can find the area of a circle. 52 00:04:05,000 --> 00:04:10,000 We cut up the circle and move the pieces around. 53 00:04:10,000 --> 00:04:13,000 Now, the area is the width times the height. 54 00:04:13,000 --> 00:04:18,000 The width is pi times the radius, and the height is the radius. 55 00:04:18,000 --> 00:04:26,000 The surface area of a cylinder is the sum of the areas of the two circles and the area of the side, which is really a rectangle. 56 00:04:26,000 --> 00:04:32,000 The volume of a cylinder is the area of the circle times the height of the cylinder. 57 00:04:32,000 --> 00:04:34,000 Now, here's the challenge. 58 00:04:34,000 --> 00:04:42,000 Find the length, height, and width of a rectangular prism that has a volume of 24 cubic inches, 59 00:04:42,000 --> 00:04:47,000 fits into an 8-inch PSA, and has as much surface area as possible. 60 00:04:47,000 --> 00:04:55,000 Find out whether a tall cylinder or a wide cylinder has more surface area when the volume stays the same. 61 00:04:55,000 --> 00:04:59,000 You can download the files for this activity from the NASA Connect website. 62 00:04:59,000 --> 00:05:04,000 It's now time for your teacher to pause the program so you can take the challenge. 63 00:05:04,000 --> 00:05:09,000 Use your imagination. Draw figures. Take measurements. Do calculations.