A plastic ball in a liquid is acted upon by its weight and by a buoyant force. T
ID: 1315857 • Letter: A
Question
A plastic ball in a liquid is acted upon by its weight and by a buoyant force. The weight of the ball is 7.1 N. The buoyant force has a magnitude of 9.4 N and acts vertically upward. At a given instant, the ball has zero velocity. At that instant, an external force acting on the ball imparts an acceleration of 3.0 m/s2 in the downward direction of the ball. The external force, including direction, is closest to:
A plastic ball in a liquid is acted upon by its weight and by a buoyant force. The weight of the ball is 7.1 N. The buoyant force has a magnitude of 9.4 N and acts vertically upward. At a given instant, the ball has zero velocity. At that instant, an external force acting on the ball imparts an acceleration of 3.0 m/s2 in the downward direction of the ball. The external force, including direction, is closest to:
2.3 N, downward 4.5 N, downward 2.3 N, upward 24 N, downward 24 N, upwardExplanation / Answer
answer is B 4.5 N, downward
F + W - Fb = ma
F + W - Fb = (W/g)a
F = (W/g)a + Fb - W
= (7.1N/9.81m/s2)(3m/s2) + 9.4N - 7.1N =4.47N (downward)
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