Chapter 12, Problem 72AP

A $40-kg$ boy jumps from a height of $3.0m$ , lands on one foot and comes to rest in $0.10s$ after he hits the ground. Assume that he comes to rest with a constant deceleration. If the total cross-sectional area of the bones in his legs just above his ankles is $3.0c{m}^2$ , what is the compression stress in these bones? Leg bones can be fractured when they are subjected to stress greater than $1.7\times {10}^{8}Pa$ . Is the boy in danger of breaking his leg?