A 76.2 kg man steps out a window and falls (from rest) 1.42 m to a sidewalk. Wha

Question

A 76.2 kg man steps out a window and falls (from rest) 1.42 m to a sidewalk. What is his speed just before his feet strike the pavement?
5.28 m/s (in m/s)

If the man falls with his knees and ankles locked, the only cushion for his fall is a 0.544 cm give in the pads of his feet. Calculate the average force exerted on him by the ground in this situation. This average force is sufficient to cause cartilage damage in the joints or to break bones.
(in N)

Explanation / Answer

v = sqrt(2 g h ) = sqrt(2 x 9.81 x 1.42)

v = 5.28 m/s

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Applying vf^2 - vi^2 = 2 a d

0^2 - 5.28^2 = 2 (a)(0.544 x 10^-2)

a = 2560.7 m/s^2

F = m a = 1.95 x 10^5 N

Ans(F)

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