Train A is moving along two parallel rail tracks towards north with speed $72 \mathrm{~km} / \mathrm{h}$ and train B is moving towards south with speed $108 \mathrm{~km} / \mathrm{h}$. Velocity of train B with respect to A and velocity of ground with respect to B are (in $\mathrm{ms}^{-1}$) :

JEE Main · 2024 · 01 Feb 2024 · Shift 2 · Kinematics

Train A is moving along two parallel rail tracks towards north with speed

72 km / h

and train B is moving towards south with speed

108 km / h

. Velocity of train B with respect to A and velocity of ground with respect to B are (in

ms^{- 1}

) :

(A)-30 and 50
(B)-50 and -30
(C)-50 and 30✓ Correct
(D)50 and -30

Answer: (C)

Solution

Taking north as positive, train A moves at

V_{A} = 72 \times \frac{5}{18} = 20

m/s and train B moves south, so

V_{B} = - 108 \times \frac{5}{18} = - 30

m/s. The velocity of B relative to A is

V_{B / A} = V_{B} - V_{A} = - 30 - 20 = - 50

m/s. The velocity of the ground relative to B is

V_{G / B} = 0 - V_{B} = 30

m/s.

JEE Main · 2024 · 01 Feb 2024 · Shift 2 · Single correct option

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