Well, I'm not even sure if freefall is the right word, but my first quandary is as followed:(adsbygoogle = window.adsbygoogle || []).push({});

If two objects fall from the same height, and one object will begin to rotate after it has been release (ie. a yoyo), while the other will not rotate, then the rotating object will accelerate slower and hit the ground after the non-rotated one because of conservation of energy (PE = translational KE + Rotational KE).

But I can't seem to justify the slower acceleration of the rotating object in the force point of view since, based on my understanding, the torque of the rotating object should not affect the net force on the CM, therefore, the net forces on the CMs of both object should be the same and the translational acceleration should then also be equal.

I know there is something wrong with my logic, but I can't find where. Any help would be much appreciated.

My second question has to do with a quote in my physics textbook: "we see that if a body is to remain at rest, the net torque applied to it (calculated about any axis) must be zero .... the choice of axis is arbitrary. If a body is at rest, then net torque = zero about any axis what so ever."

What I do not understand is why can the axis be arbitrary is definition of torque is force times distance to the axis? For example, if a large rigid stick has two equally strong torque of opposite direction acting on the two ends and one force that cancel out the translational effect of the torque acting on the CM, then the stick will remain at rest if and only if the axis of rotation is the CM, otherwise, the torque will be unbalanced and it will spin.

Any clarification is again, much appreciated. Thanks

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# Rotational Freefall and Designation of Axis

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