If the man falls with his knees and ankles locked, the only cushion for his fall is a 0.480 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.

The average force exerted on the man by the ground therefore is 153.319.53 N

Explanation:

Given the following information

Mass of man, m = 75 kg

height of fall, h = 0.48 cm

velocity just before landing,  v = 4.43 m/s

We therefore have

The work required to break the fall is equal to the kinetic energy of motion, just before touching the ground

Work done = Energy to absorb Kinetic Energy KE = 0.5·m·v²= F·h

Where:

F = Force required to break the fall

Therefore the force, F = (0.5·m·v² )/h

= 0.5×75 kg ×(4.43 m/s)²/(0.0048 m) = 153319.53 N

The average force exerted on him by the ground is therefore

= 153319.53 N.

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach