A boat can move at 5 m/s relative to the water in any direction

PHYSICS · Single correct · AP · Physics 1: Algebra-based · Kinematics · Kinematics

Problem

A boat can move at 5 m/s relative to the water in any direction. A river 300 m wide flows due east at 2 m/s. A dock is located on the opposite bank 400 m downstream (east) from the boat’s starting point. To arrive at the dock in the shortest possible time, the boat should be steered so that its velocity makes an angle θ\theta (measured downstream from the straight-across direction). Which angle is closest to the optimal value of θ\theta? (a) 67∘ downstream67^{\circ}\text{ downstream} (b) 39∘ downstream39^{\circ}\text{ downstream} (c) 23∘ downstream23^{\circ}\text{ downstream} (d) 53∘ downstream53^{\circ}\text{ downstream}

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