A piece of wood is taken deep inside a long column of water and released. It will move up
A piece of wood is taken deep inside a long column of water and released. It will move up
(a) with a constant upward acceleration
(b) with a decreasing upward acceleration
(c) with a deceleration
(d) with a uniform velocity.
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(b) with a decreasing upward acceleration
Explanation:
Just when the wood is released, the net force on it is B-W, {Buoyancy minus weight}upward. If the mass of the wood be m, then it has an initial acceleration a =(B-W)/m. But as the velocity increases the viscous force V acts downward. So the net force becomes B-W-V. Though B and W are constant, V increases with the velocity. Thus as the wood moves up, the net force and hence the acceleration decreases.
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