A boy runs horizontally with speed v while water falls vertically downward with speed u. At what angle θ to the vertical should he incline a long hollow tube so that water enters without touching the sides?
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Question

A boy runs horizontally with speed v while water falls vertically downward with speed u. At what angle θ to the vertical should he incline a long hollow tube so that water enters without touching the sides?

Options

G1 Physics · Accepted Answer

Relative water velocity has horizontal component v opposite to the boy and vertical component u downward. Angle from vertical satisfies tanθ=v/u. Hence θ=tan⁻¹(v/u). Option A.