Even if we have to displace an object to a small distance, the object needs to have kinetic energy but when my teacher told me that there's no work done in rotating an object around the center, it really confused me. I understand mathematically why there's no work being done by the centripetal force but it doesn't reason to me why an object goes on rotating with no kinetic energy involved?
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1$\begingroup$ It isn't clear that your teacher is right. This may help. Is work done in rolling friction? $\endgroup$– mmesser314Commented Jun 14, 2021 at 14:21
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2 Answers
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The kinetic energy is constant when something moves in a circle at constant speed.
The 'Work done' formula is $W=Fd$, where $d$ is the distance moved in the direction of the force. But since the centripetal force and distance moved by the object are always at right angles, for circular motion, then no work is done.
It's true that some work would have to be done on the object to give it the kinetic energy in the first place, but once it has it and is moving in circular motion, no more work needs to be done to keep it going.
answered Jun 14, 2021 at 14:08
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Your teacher should have, perhaps, explained accelerating the angular velocity would require work. Maintaining a constant angular velocity, when no friction or drag is involved, requires no additional work.
answered Jun 14, 2021 at 16:34