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A block of wood is pushed far below the surface in a tall column of water and then let go. As it rises, it moves
- with a constant upward acceleration
- with an upward acceleration that decreases
- with a deceleration (slowing down)
- at a constant (uniform) velocity
Correct answer: with an upward acceleration that decreases
Solution
Just after release the only forces are buoyancy (constant) and weight (constant), giving an initial upward acceleration. As the block speeds up, the viscous/drag force grows and opposes motion, so the net upward force and hence the acceleration decreases (until terminal velocity).
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