At the Aircraft Landing Dynamics Facility located at NASA\'s Langley Research Ce

Question

At the Aircraft Landing Dynamics Facility located at NASA's Langley Research Center in Virginia, a water-jet nozzle propels a 46,000 kg sled from zero to 400 km/hour in 2.5 seconds. (This sled is equipped with tires that are being tested for the space shuttle program, which are then slammed into the ground to see how they hold up.) (a) Assuming a constant acceleration for the sled, what distance does it travel during the speeding-up phase? (b) What is the net work done on the sled during the time interval?
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A cat stands on a skateboard that moves without friction along a level road at a constant velocity of 2.00 m/s. She is carrying a number of books. She wishes to stop, and does so by hurling a 1.20 kg book horizontally forward at a speed of 15.0 m/s with respect to the ground. (a) What is the total mass of the cat, the skateboard, and any remaining books? (b) What mass book must she now throw at 15.0 m/s with respect to the ground to move at -2.00 m/s?
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You, a 50.0 kg skier, have a flat 12.0 meter long runway leading up to the lip of the canyon. In that stretch, you must apply a force such that at the end of the straightaway, you are traveling with a speed of 8.00 m/s. Any slower, and your jump will fall short. Any faster, and you will overshoot.
How much force must you apply, in newtons, over the 12.0 meter flat stretch? Ignore other forces like friction and air resistance.

Explanation / Answer

Given: mass of the skier m = 50 kg distnce of run way = 12 m speed v = 8 m/sec distanc have to stretch l = 12 m ......................................................................................................... Force F = m / t m = change in momentum       = mv       = 50 kg * 8.00 m/sec       = 400 kg.m/sec time t = distace / speed          = 12 m / 8 m/sec          = 1.5 sec so required force F = 400 kg.m/sec / 1.5 sec                                 = 266.6 Newtons. NOTE: post remaining as seperate.

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