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free body diagram for pulley


The only two forces acting on the pulley are the two tensions. What's the net torque? The torque from tex2html_wrap_inline814 is the cross product of the radius vector with tex2html_wrap_inline820 . This points into the page, which is the negative tex2html_wrap_inline822 direction. The torque from tex2html_wrap_inline812 points the opposite way, in the positive tex2html_wrap_inline822 direction. So in the z-direction


Now we apply tex2html_wrap_inline828 in the z-direction.


Joshua Deutsch
Sun Feb 23 15:54:50 PST 1997