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Old May 26th 2010, 05:03 AM   #1
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Join Date: Apr 2008
Posts: 6
Rotation about Fixed Axis

Here's my question:
A uniform rod AB of mass m is released from rest when it is at 60degrees from the surface of the earth. Assuming the friction force between end A (that's the end that touches the surface) and the surface is large enough to prevent sliding, determine (for the instant just after release)
a) Angular acceleration of the rod
b) The normal reaction and the friction force at A.

This seems like (and probably is) an easy sum, but I'm pretty sure I'm screwing up.

I got part a). It's 3g/4L. The answer matches with the one given.

However, I don't know what to do about part b). I think one equation will be mg - N giving me the net torque in the clockwise direction. But, I'm not sure if the sin and cos components have to be taken or what?
The other one should probably be friction balancing out the net force.

Any help is appreciated. Thank you.

Last edited by Ruler of Hell; May 26th 2010 at 05:15 AM. Reason: Typo.
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