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**1. The question**

This question is about the design of a car seat belt. The seat belt restraints a passenger when the car is involved in an accident.

Use definitions of stress and strain to show that

*stress x strain*has the same units as

*energy stored per unit volume of seat belt*.

## Homework Equations

Deriving question hence no specific equation required.

## The Attempt at a Solution

stress x strain = force/area x extension\length = Nm/m^3 = N/m^2 = Nm^(-2)

energy stored per unit volume of seat belt = J/m^3

**4. The problem occurring**

I am not getting the same unit so it's contradicting the question. Can I have help as to where I have gone wrong. Thanks in advance.