Thread: Physics Quiz
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Unread 18-11-2011, 23:18
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Re: Physics Quiz

Quote:
Originally Posted by Ninja_Bait View Post
If the torque was high enough and the wheel was free to move, would it be moving in the positive y or negative?
The wheel is free to move... as soon as enough torque is applied to overcome the static friction on the floor.

I forgot to clarify the direction of the torque being applied to the wheel. So here goes:

Assume that the torque being applied to the wheel is in the direction to try to make the wheel travel counter-clockwise around the pivot.


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I'm going to assume the positive case.
Yes, counterclockwise.


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Off the top of my head the forces on the wheel I can think of are the tension in the rod, the torque from the motor, the friction, the weight and the normal. Am I missing anything?
Do a free-body diagram of the wheel+motor assembly, and just consider all the external forces acting on that assembly in the horizontal plane. So all you need to consider are the tension in the rod and the friction force of the floor acting on the wheel.


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Also, it sounds like the wheel is in static equilibrium
Correct. The problem specified that the torque was not sufficient to overcome the static friction.


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so I think the friction points somewhere in the southeast direction...
A common mistake. Think free-body diagram, and make the forces balance in the horizontal plane.


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I hate physics.
Say it ain't so! You're doing great so far.