Two cars A and B each of mass $10^{3} \mathrm{~kg}$ are moving on parallel tracks separated by a distance of 10 m , in same direction with speeds $72 \mathrm{~km} / \mathrm{h}$ and $36 \mathrm{~km} / \mathrm{h}$. The magnitude of angular momentum of car A with respect to car B is $\_\_\_\_$ J.s.

JEE Main · 2026 · 21 Jan 2026 · Shift 2 · Rotational Mechanics

Two cars A and B each of mass

1 0^{3} kg

are moving on parallel tracks separated by a distance of 10 m , in same direction with speeds

72 km / h

and

36 km / h

. The magnitude of angular momentum of car A with respect to car B is

____

J.s.

(A) $3.6 \times 1 0^{5}$
(B) $1 0^{5}$ ✓ Correct
(C) $3 \times 1 0^{5}$
(D) $2 \times 1 0^{5}$

Answer: (B)

Solution

Angular momentum of A with respect to B is

L = m v_{r e l} r_{⊥}

, where

v_{r e l}

is the relative velocity and

r_{⊥}

is the perpendicular distance.

v_{r e l} = 72 - 36 = 36

km/h

= 36 \times \frac{5}{18} = 10

m/s.

L = 1000 \times 10 \times 10 = 1 0^{5}

kg·m²/s.

JEE Main · 2026 · 21 Jan 2026 · Shift 2 · Single correct option

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