JEE Main · 2026 · 04 Apr 2026 · Shift 2 · Kinematics

Two cars A and B are moving in the same direction along a straight line with speeds

100 km / h

and

80 km / h

, respectively such that car A is moving ahead of car B . A person in car B throws a stone with a speed v so that it hits the car A with a speed of

5 m / s

. The value of v is

____

km / h

(A)18
(B)28
(C)38✓ Correct
(D)48

Answer: (C)

Solution

The stone must strike car A with a relative speed of

5 m/s = 18 km/h

. Taking the common direction of motion as positive, the stone has to overtake A, so its ground speed

V_{s}

satisfies

V_{s} - 100 = 18

, giving

V_{s} = 118 km/h

. The stone is launched from car B, which moves at

80 km/h

, so its speed relative to B is

v = V_{s} - 80 = 118 - 80 = 38

. The required throwing speed is

38 km/h

JEE Main · 2026 · 04 Apr 2026 · Shift 2 · Single correct option

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