# Biophysics Problem 30

For the human tibia bone the ultimate tensile strength (the point at which fracture occurs) is $1.4 \times 10^8 \; N\; m^{-2}.$ What is the strain at the point of fracture? Assume that Hooke's Law is valid up to the point of fracture.

#### Calculations

Recall Hooke's Law:

$\text{stress} = Y \times \text{strain}$

where $Y = 2 \times 10^{10}\; N/m^2$ (found on page 103 of your textbook).

In this case, the stress is the ultimate tensile strength. You should be able to make a direct substitution, and get:

$\text{strain} = 7 \times 10^{-3}$ (Note that this is a dimensionless ratio.)