Source: Extra Practice

Which of the following physical quantities has the same dimensions as Planck's constant (hh)?

Options

Option A

Energy

Option B

Momentum

Option C is correct

Angular Momentum

Option D

Power

Explanation

Let's determine the dimensions for each quantity:

  1. Planck's constant (hh): From E=hνE = h\nu, where EE is energy and ν\nu is frequency. [h]=[E][ν]=[ML2T2][T1]=[ML2T1][h] = \frac{[E]}{[\nu]} = \frac{[ML^2T^{-2}]}{[T^{-1}]} = [ML^2T^{-1}].
  2. Energy (EE): [ML2T2][ML^2T^{-2}].
  3. Momentum (pp): p=mvp = mv, so [p]=[M][LT1]=[MLT1][p] = [M][LT^{-1}] = [MLT^{-1}].
  4. Angular Momentum (LL or JJ): L=Iω=mr2ωL = I\omega = mr^2 \omega, or L=r×pL = r \times p. [L]=[L][MLT1]=[ML2T1][L] = [L][MLT^{-1}] = [ML^2T^{-1}].
  5. Power (PP): P=W/tP = W/t, so [P]=[ML2T2][T]=[ML2T3][P] = \frac{[ML^2T^{-2}]}{[T]} = [ML^2T^{-3}]. Comparing the dimensions, Planck's constant [ML2T1][ML^2T^{-1}] has the same dimensions as Angular Momentum [ML2T1][ML^2T^{-1}].