⚛️ Physics · Motion in a Plane · NEET & JEE

A swimmer whose speed relative to water is 6 m/s must cross a 60 m wide river flowing at 3 m/s and reach the point directly opposite. He should aim upstream, measured from the line straight across, at an angle of:

Answer: 30.

A 45°
B 60°
C 30°
D 53°

Correct answer: C. 30°

Explanation: The upstream component must cancel the current: 6 sinθ = 3, so sinθ = 0.5 and θ = 30°.

Projectile trajectories launched at 15, 30, 45, 60, 75 and 90 degrees at the same speed, each annotated with range R, maximum height H and time of flight T, with coloured dots marking equal time intervals

Projectiles at equal speed: range is maximum at 45°, and complementary angles (30° and 60°) share the same range. Image: Cmglee, CC BY-SA 3.0, via Wikimedia Commons.

Concept context

Vectors, projectile motion, uniform circular motion, and relative velocity - the foundation of 2D kinematics for NEET and JEE.

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A swimmer whose speed relative to water is 6 m/s must cross a 60 m wide river flowing at 3 m/s and reach the point directly opposite. He should aim upstream, measured from the line straight across, at an angle of:

Concept context

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