Calculate the force needed to stop the downward motion of a jogger\'s leg, if hi

Question

Calculate the force needed to stop the downward motion of a jogger's leg, if his leg has a mass of 12.0 kg, a speed of 6.00 m/s, and stops in a distance of 1.40 cm. (Be certain to include the weight of the 75.0 kg jogger's body.)

Note: The answer to this particular problem is 16200 N. Please provide a detailed explanation on how to find this answer! I know this seems like a simple problem but I can't seem to figure it out, I've tried using the formula Vf^2 = Vi^2 + 2ad to find acceleration, then F=ma to find force but keep coming up with the wrong answer.

Explanation / Answer

Fnet =Fa-mg......

work energy theorem......

W=-Fnet.S.....

(1/2)*ml[V^2-U^2] = -Fnet.S=-[Fa-mg].S......

V=0 and ml=12kg......m=75 kg    g=9.8    s=0.014m   u=6m/s......

solving we get...

Fa=16193 N====16200 N approximately

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