Question

Which of the following pairs of physical quantities has different dimensions

• A. stress, pressure
• B. Young’s modulus, energy density
• C. density, relative density
• D. energy, torque

Answer 1

The correct option is C density, relative density

Density and relative densities dimension formulas are not same.
Because density is given by $\frac{M}{V}=M^1{L}^{–3}{T}^0$
but
relative density $=\frac{\text{density of body}}{\text{density of some reference body}}$ has no dimensions.