# Belt friction - determining angles

1. Nov 9, 2008

### O011235813

1. The problem statement, all variables and given/known data
A cable passes around three 2-in-radius pulleys and supports 2 blocks as shown. Pulleys C and E are locked to prevent rotatoin, and the coefficient of friction between the cable adn the pulleys are static = .20 and kinetic = .15. Determine the range of value of the weight of black A for which equilibrium is maintained (a) if pully D is locked, (b) if pully di is free to rotate.

2. Relevant equations

ln(T2/T1) = static * angle

3. The attempt at a solution

The main problem i'm having is determining the angles to be used. I can see it's a 30/60/90 triangle. So i tried using pi/3 for the D and pi/6 for C, and that didn't work.

Then i used pi/3 still for D and changed pi/6 to 2*pi/3. And that didn't work. If anyone could help me with just the angles that'd be much appreciated. I think i have everything after that down. Thanks for all the help :D

2. Nov 9, 2008

### O011235813

sorry the image didn't show up ... let me try this

3. Nov 9, 2008

### O011235813

nvm i figured it out :D

4. Nov 9, 2008

### O011235813

actually...now that i'm trying to figure out the 2nd part....i can't get it...do i have to use a couple system at D or something of that sort? use moments? or am i over thinking it? thanks once again for any help :D