A ball thrown vertically upward is momentarily at rest at its highest point. Why is it not in equilibrium there?
ABecause its velocity is zero
BBecause no force acts on it at the top point
CBecause a downward net force equal to its weight still acts on it
DBecause its acceleration is upward
Answer & Solution
Correct answer: C. Because a downward net force equal to its weight still acts on it
Equilibrium requires zero net force. At the highest point, the ball's velocity becomes zero only instantaneously, but gravity still acts downward, so the net force is not zero. Therefore it is not in equilibrium and starts moving downward.
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