Thread: Rod in freefall
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A.T.
#5
Nov22-12, 06:42 AM
P: 3,867
Quote Quote by aaaa202 View Post
But now put a coordinate frame on one of the end points. Apart from the gravity pulling down on the rod as a whole, there will now be a net torque on the rod (because gravity acts in the center of mass).
In an accelerated frame that falls with the rod, there is an inertial force upwards:
http://en.wikipedia.org/wiki/Fictiti..._straight_line

The inertial force cancels gravity at any point of the rod. Regardless if the origin is in the center or the end: There is no net force on any part of the rod in such a frame, and thus no torque.