1 00:00:00,000 --> 00:00:03,500 Hi RJ, Bianca's mom said you'd be coming by, how can I help you? 2 00:00:03,500 --> 00:00:06,800 We need to learn more about pulleys. What exactly is a pulley? 3 00:00:06,800 --> 00:00:11,000 Well, a pulley is a simple machine. It's made from a rope and a wheel. 4 00:00:11,000 --> 00:00:13,000 It makes lifting objects easier. 5 00:00:13,000 --> 00:00:14,000 How does it do that? 6 00:00:14,000 --> 00:00:16,000 It changes the direction of the force. 7 00:00:16,000 --> 00:00:20,000 For example, if you're lifting a heavy object off the floor, 8 00:00:20,000 --> 00:00:22,000 using a pulley mounted to the ceiling, 9 00:00:22,000 --> 00:00:25,000 you can pull down the rope instead of pushing up. 10 00:00:25,000 --> 00:00:28,000 Aren't you using the same amount of force needed to lift an object? 11 00:00:28,000 --> 00:00:32,000 Good question. Yes you are, but it's easier to pull down than to push up. 12 00:00:32,000 --> 00:00:36,000 So how would I reduce the amount of force needed to lift a heavy object? 13 00:00:39,000 --> 00:00:42,000 If you add a second pulley and you support the load with two ropes, 14 00:00:42,000 --> 00:00:45,000 then you only need half of the force to lift it. 15 00:00:45,000 --> 00:00:49,000 What if you add a third pulley and support the load with three ropes? 16 00:00:49,000 --> 00:00:53,000 If you divide the weight of the object by the number of ropes supporting the load, 17 00:00:53,000 --> 00:00:56,000 then you can determine what kind of force you need to lift the object. 18 00:00:56,000 --> 00:01:00,000 Awesome. So what do you use pulleys for here at NASA Langer Research Center? 19 00:01:00,000 --> 00:01:05,000 As an aerospace engineer and a Level 3 manager of NASA's Aviation Safety Program, 20 00:01:05,000 --> 00:01:08,000 I use pulleys in crashworthiness research. 21 00:01:08,000 --> 00:01:10,000 What's crashworthiness? 22 00:01:10,000 --> 00:01:14,000 Crashworthiness is how well an aircraft protects occupants in a crash. 23 00:01:14,000 --> 00:01:18,000 A team of engineers and I conduct tests and analysis on materials, 24 00:01:18,000 --> 00:01:20,000 on aircraft structures and full-scale aircraft. 25 00:01:20,000 --> 00:01:22,000 Why is that important? 26 00:01:22,000 --> 00:01:25,000 In a real crash, it is very difficult to understand the damage 27 00:01:25,000 --> 00:01:27,000 because many things are destroyed. 28 00:01:27,000 --> 00:01:31,000 By conducting controlled crash tests, we can better understand what happens in a real crash, 29 00:01:31,000 --> 00:01:36,000 and then we can develop better designs that will protect the passengers. 30 00:01:36,000 --> 00:01:38,000 You crash real airplanes here? 31 00:01:38,000 --> 00:01:40,000 We sure do, right here at the gantry. 32 00:01:40,000 --> 00:01:42,000 What exactly is the gantry? 33 00:01:42,000 --> 00:01:46,000 The gantry is the Impact Dynamics Research Facility where we perform full-scale crash tests. 34 00:01:46,000 --> 00:01:50,000 It was also used by astronauts during the Apollo missions to practice landing on the moon. 35 00:01:50,000 --> 00:01:53,000 That's cool. How do you crash planes? 36 00:01:53,000 --> 00:01:56,000 A test vehicle is suspended from two swing cables, 37 00:01:56,000 --> 00:02:00,000 pulled back and released to allow the test vehicle to swing into the impact surface below. 38 00:02:00,000 --> 00:02:04,000 The swing cables are pyrotechnically separated from the vehicle just prior to the impact 39 00:02:04,000 --> 00:02:07,000 so that free flight conditions are established. 40 00:02:07,000 --> 00:02:10,000 Airplanes are really heavy. You must need a lot of pulleys. 41 00:02:10,000 --> 00:02:13,000 Actually, we only use one pulley, but it's a pretty big pulley. 42 00:02:13,000 --> 00:02:15,000 How much can you lift? 43 00:02:15,000 --> 00:02:17,000 We currently can only lift up to 30,000 pounds 44 00:02:17,000 --> 00:02:20,000 because that's the maximum capacity of the gantry's bridge. 45 00:02:20,000 --> 00:02:22,000 How can you lift 30,000 pounds? 46 00:02:22,000 --> 00:02:27,000 I run steel rope from the lifting device through the pulley and then attach it back to the bridge. 47 00:02:27,000 --> 00:02:30,000 The pulley is attached to the aircraft. This is called double hitching. 48 00:02:30,000 --> 00:02:32,000 30,000 pounds is a lot of weight. 49 00:02:32,000 --> 00:02:35,000 Yes, it is, but we don't need 30,000 pounds of force to lift it. 50 00:02:35,000 --> 00:02:39,000 With one pulley attached to the aircraft, you have two ropes supporting the load. 51 00:02:39,000 --> 00:02:42,000 Then you only need 15,000 pounds of force. 52 00:02:42,000 --> 00:02:45,000 Alfred and Jacob doesn't weigh 30,000 pounds, 53 00:02:45,000 --> 00:02:48,000 so I bet we could use pulleys to lift them with no problem at all. 54 00:02:48,000 --> 00:02:49,000 Thanks, Mrs. Jones. 55 00:02:49,000 --> 00:02:51,000 You're welcome and good luck. Call if you need anything. 56 00:02:51,000 --> 00:02:52,000 Okay.