Free Body Diagram of Pulley with Friction

[sean882]

Homework Statement

Draw a freebody diagram of the fixed pulley used in your lab.

I am trying to get ahead in my statics class so I can start preparing for finals, but we haven't covered this in class yet, and it is not in our textbook. Our lab section is a bit ahead of our lecture section. If you could please help me as far as how to correctly show the forces, I would much appreciate it.

At the end of Ts and TL are masses; TL is a set mass, and Ts is a the mass at which the system just barely overcomes static friction and starts to move. The end goal is to calculate the coefficient of friction in the fixed pulley. The only trouble I am having is part a.), which requires us to draw a free body diagram. I need a little assistance with how to include the force of friction into this diagram.

This is a fixed pulley, i.e., it does not rotate. It is as if you superglued the center of a normal pulley, so it will no longer rotate.

I am not sure what forces must be shown on this freebody diagram. Of course the T$$\underline{}S$$ and T$$\underline{}L$$ will need to be shown, as well as the angle $$\vartheta$$ but I am unsure how to show the force of friction in the fbd of the pulley.

Also, would it be necessary to show a moment?

Thank you for your help. Below is a rough diagram made in MS Paint with my attempt so far.[PLAIN]http://img215.imageshack.us/img215/842/31808471.jpg

The Attempt at a Solution

 

[donutz610]

When i have trouble with free body digrams i do the following:
First draw your your force of gravity, then find the normal force of the system, the one that counteracts gravity. Then break up the two masses into their sine and cosines based on there angles. Put these on the free body diagram to help you form an idea of what forces are going in which directions.

 

[sean882]

Thanks for your help.

I guess a better way to phrase my question would be, where abouts on the pulley would be the proper place to show the force of friction on the circle? My inclination is directly opposite of Ts.

 

[panchoman]

tangent and opposite to the way which the rope will move, so if the rope will move to the right, then the force of friction will also be tangent to the same point where the rope is moving(top of the pulley), and will be pointed to the left..

someone correct me if I'm wrong..

 

[sean882]

Thank you so much!



-Sean