A stunt person whose mass is 62.5 kg falls from rest vertically downward a dista

Question

A stunt person whose mass is 62.5 kg falls from rest vertically downward a distance of 8.10 m.
The person's fall is not 'free-fall' due to air resistance. The person's speed is 10.5 m/s just before hitting an air bag (that stops the fall).

A) Determine the change in the kinetic energy of the person during the stunt.

B) Determine the work done by the force of gravity on the stunt person.

C) Determine the total work done on the stunt person.

D) Determine the work done by air resistance on the stunt person.

Explanation / Answer

A)

Here ,

change in kinetic energy , = final KE - initial KE

change in kinetic energy , = 0.5 * 62.5 * 10.5^2 - 0

change in kinetic energy = 3251.25 J

B)

work done by gravity = mgh

work done by gravity = 62.5 * 9.8 * 8.10

work done by gravity = 4961.25 J

C)

using work energy theorum

, total work done = change in kinetic energy

total work done = 3251.25 J

D)

Work done by gravity + work done by air resistance = total work done

4961.25 + work done by air resistance=3251.25

work done by air resistance = 1710 J

the work done by air resistane is 1710 J

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