A paratrooper pilot fell 370 m after jumping without his parachute opening. He landed in a snowbank, creating a crater 1.2 m deep, but survived with only minor injuries. Assume the pilot's mass was 84 kg and his terminal velocity was 30 m/s.
(a) Estimate the work done by the snow in bringing him to the rest.
(b) Estimate the average force exerted on him by the snow to stop him.
(c) Estimate the work done on him by the air resistance as he fell.
For part A, I tried 1/2mv^2, and it didn't work.
(a) Estimate the work done by the snow in bringing him to the rest.
(b) Estimate the average force exerted on him by the snow to stop him.
(c) Estimate the work done on him by the air resistance as he fell.
For part A, I tried 1/2mv^2, and it didn't work.
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Hello
a)
The work done by the snow is equal to the kinetic energy of the person before hitting the snow:
work = 1/2*mv^2 = 1/2*84*30^2 = 37 800 Nm.
If this is what you did, and it is wrong, I do not know why it should be wrong.
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b)
find the time needed to stop him:
v^2 = 2as
a = v^2/2s
a = 900/2,4
a = 375 m/s^2
s = 1/2*at^2
1.2 = 1/2*375t^2
t^2 = 2.4/375
t = 0.08 s
And force = momentum/time
F = 85 kg*30 m/s /0.08 s
F = 31 875 N
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c)
the initial potential energy was
Epot = mgh = 85*9.8*370 = 308 524 Nm
the final kinetic energy was 37 800 Nm
The difference = 270 724 Nm is the work done by air resistance
Regards
a)
The work done by the snow is equal to the kinetic energy of the person before hitting the snow:
work = 1/2*mv^2 = 1/2*84*30^2 = 37 800 Nm.
If this is what you did, and it is wrong, I do not know why it should be wrong.
-----
b)
find the time needed to stop him:
v^2 = 2as
a = v^2/2s
a = 900/2,4
a = 375 m/s^2
s = 1/2*at^2
1.2 = 1/2*375t^2
t^2 = 2.4/375
t = 0.08 s
And force = momentum/time
F = 85 kg*30 m/s /0.08 s
F = 31 875 N
---------
c)
the initial potential energy was
Epot = mgh = 85*9.8*370 = 308 524 Nm
the final kinetic energy was 37 800 Nm
The difference = 270 724 Nm is the work done by air resistance
Regards