Question

Which of the following is dimensionless quantity?

• A. Strain
• B. Stress
• C. Quantity of heat
• D. Specific heat

Answer 1

Answer: (A)

Strain

Answer 2

The dimensionless quantity is Strain.

Strain is defined as the measure of the extent of deformation of an object due to an externalforce. Strain helps determine the change in the dimension being measured or the relative change of length/area/volume. The strain is expressed as, $\frac{\Delta L}{L}$ where L is the initial length and $\Delta$L is the change in length after deformation.
Dimension for Change in the length = [M0 L1 T0]
Dimension for Original length = [M0 L1 T0]

Therefore, the dimension of Strain = [M0 L1 T0]/ [M0 L1 T0]= [M 0 L0 T0]

Thus, **strain is a dimensionless quantity. **

Read More:Dimensional Analysis