# Biophysics Problem 32

If the leg bones described in Question 31 are $90 \;cm$ long, what is the amount of compression in each leg at the fracture point? Assume that the leg bones remain elastic under compression until fracture, which occurs at a stress of $1.4 \times 10^8\;N\;m^{-2}.$

#### First Step

Hooke's Law applies in compression (as in this problem) as well as in tension.

From the table on page 103 of your text, $Y = 2 \times 10^{10} \;N\; m^2.$

You should be able to substitute and calculate the change of length now. (In the above formula, $L$ is the leg length).

#### Calculations

The stress was given in the problem, and the leg length is $0.9 \;m.$

You should have found that $L = 0.0063 \;m.$