Practice question · Select all that apply
A stone is whirled in a horizontal circle at a constant speed of 5 m/s. Select every statement that is TRUE.
Hints
- Speed is a magnitude; velocity is a vector carrying a direction as well.
- If the velocity vector changes at all, its derivative is not zero.
Show the answer
- C. It is accelerating
- D. Its speed is constant
- E. The direction of its velocity is changing
Why
Constant speed with changing direction means the velocity vector is changing, and acceleration is the rate of change of that vector, so the stone is accelerating even though its speedometer never moves. Treating 'constant speed' as 'no acceleration' is the trap this question is built around.
Practise Kinematics and the Language of Motion
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