1. The problem statement, all variables and given/known data I have a system that looks like this: http://dept.physics.upenn.edu/courses/gladney/phys1/homework/images/half_Atwood.gif [Broken] m2 mass is 0.07kg. The m1 mass is gradually increased. Basically, if you tap it, m2 starts moving by itself at constant speed when m1 is at 0.03kg. What is the coefficient of static friction? 2. Relevant equations F=ma Fmax=mu * Fn 3. The attempt at a solution First I drew a free body diagram. The mass on the table is being pulled to the right with a force of (9.8)(0.03kg) = 0.294N. So basically the static force has to be equal that going the other way. Then I did the F=ma for the mass on the table, and for it to move it would need F= mu * 0.686N. So we can solve for 0.294N = mu * 0.686N, giving a coefficient of friction of 0.428. Is this right? I am not sure if I am thinking of this the right way.