## College Physics (4th Edition)

Strain is $\frac{\Delta L}{L}$ so it has a dimensionless unit. However, Young's modulus, stress, and ultimate strength are not measured in dimensionless units, so the answer is not (a), (b), or (d). Young's modulus is measured in units of $Pa$ which can be expressed as $N/m^2$ Stress is a measure of the force per unit area so it is measured in units of $N/m^2$ The correct answer is: (c) Young's modulus and stress