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posted by  sooner_fan_89 on 11/4/2009 11:57:55 PM  |  status: Live  |  Earned Karma: 25

Work

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N/A N/A N/A N/A 11/5/2009 at 5:00:00 AM
Question Details:
An airplane pilot fell 365 m after jumping from an aircraft without his parachute opening. He landed in a snowbank, creating a crater 1.3 m deep, but survived with only minor injuries. Assuming the pilot's mass was 75 kg and his terminal velocity was 50 m/s, estimate the following.
(a) the work done by the snow in bringing him to the rest
(b) the average force exerted on him by the snow to stop him
(c) the work done on him by the air resistance as he fell
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posted by Mobiusdick on 11/5/2009 12:18:33 AM  |  status: Live
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Response Details:
a) Using his terminal velocity, we can say that the pilot's Kinetic energy at impact was
KE = (1/2)(75kg)(50m/s)2 = 93750 J
The work done to stop him must equal this energy.
W = 93750 J

b) Average Force:
F = W/d = 93750J/1.3m = 72115.38 N

c)The work done by air resistance is equal to the energy lost during the fall. At the beginning he has just potential energy, and at the bottom, just kinetic. The difference between them is the work.

PE - KE = W
(m)(g)(h) - (1/2)(m)(v2) = W
(75)(9.8)(365) - (1/2)(75)(502) = 174525 J
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