In the above videos we show how a pointlike object, which can rotate around
a fixed axis
to which it is attached by a massless rod,
is accelerated by a force F
which is applied over an angle of 2π.
We apply forces of the same intensity
to the object in both videos.
Nevertheless, the lefthand video shows a larger acceleration
than the righthand video.
The difference in acceleration stems from the position
where the force is applied.
Let us define the distances, from the rotation axis to the position
where the force is applied, by
r1
for the lefthand video and by
r2
for the righthand video (r2 < r1).
Then the work done by the force F
equals 2πr1F in the lefthand video
and 2πr2F in the righthand video.
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