Practice question · Multiple choice
A ball thrown straight up is momentarily motionless at the top of its flight. What is its acceleration at that instant?
Hints
- Acceleration is the rate of change of velocity. Is the velocity changing at the top?
- If acceleration were zero there, what would the ball do next?
Show the answer
C. 9.8 m/s² downward, unchanged, since gravity never stops acting
Why
Velocity is zero and its rate of change is not, a moment later the ball is moving downward, which could not happen under zero acceleration. Confusing 'not moving' with 'not accelerating' is the classic kinematics error, and this instant is where it is most tempting.
Practise Kinematics and the Language of Motion
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