1. The problem statement, all variables and given/known data http://media.collegeboard.com/digitalServices/pdf/ap/apcentral/ap13_frq_physics_c_mechanics.pdf The problem is above. It is number 3. The solutions are below: http://media.collegeboard.com/digit...entral/ap13_physics_cm_scoring_guidelines.pdf 2. Relevant equations Torque= I * angular acceleration, F=ma 3. The attempt at a solution My questions are the following: Why do they in part a of the solution do the expression 2Fa-mg=0? I understand that they have Fa acting on the object and mg, but why do they have the left rope's tension equal Fa? And then in part B, why do they have the expression Fa + T - Mg = Ma, meaning why do they have Fa != T. And then they substitute the T from the torque equation. Why is doing the problem in this manner necessary, with a separate value for T, which does not equal Fa?