Hello: I've attached a drawing of the problem (pretend that the circular things are pulleys, and the strings are straight). A person of mass M stands on a platform of mass m and pulls himself up by 2 ropes which hang over pulleys, as in the attachment. he pulls each rope with force F and accelerates upward with uniform acceleration a. Find a. So I think we can say that the length of the strings over these pulleys can be let D = distance between the pulleys let R = radius of pulleys X + D + 2piR + Z + X + D + 2piR + Y = L, where L, R, D are constant. I think Z = (X - h), where h = the length of ceiling to pulley. So if we take the second derivative we have: 2*d2X/dt2 + d2Z/dt2 + d2Y/dt2 = 0. I am not sure if that's correct ... and not sure what to do after that? I think that the force is the same for both sides. How do I find the relationship between the acceleration of Z and Y? Would they be the same since the pulleys are massless and if they weren't the same the platform wouldn't be level? Thanks.