I'm reviewing my physics and it's been over a year since I took a course in it. My textbook does have the solutions, but I have a tendency to do it my way. My solution is quite different, but the answer matches up, yet would my answer be correct? 1. The problem statement, all variables and given/known data Two blocks are in static equilibrium. (I'll describe the picture.) One block (A) is 15 kg on the table, and it has a string going through a pulley which is connected to a block (B) that is dangling and is of unknown weight. a) Determine the maximum mass of block B. Coefficient of static friction mu_s = 0.20 b) If an extra 5 kg are added to B, find the acceleration of A and the tension T in the rope. mu_k = 0.14. 2. Relevant equations F = muF_N F = ma 3. The attempt at a solution a) Determine the maximum mass of block B. Coefficient of static friction mu_s = 0.20 The way I see it is that gravity is going to pull block B which will exert tension on the pulley to pull block A to the right. But friction is working against it in the negative direction. Now, if we consider that the force block B is exerting on block A should sum to zero, we have: F(due to gravity pulling on B) + F(friction working against the force of B) = 0 mg + (mu)F_N = 0 10m - 0.20(15*10) = 0 10m = 0.20*150 10m = 30 m = 3 The book says my answer is correct, but I want to make sure the way I understand it is correct. b) If an extra 5 kg are added to B, find the acceleration of A and the tension T in the rope. mu_k = 0.14. Nearly similar reasoning as above in that block B will exert some rightwards force on A while friction is working against it (but now we're moving), I'll consider just the movement of A because the acceleration of A and B should be the same magnitude by different direction. BUT it would come in useful here to use F = ma to solve for a. Considering the force in terms of one dimension only (horizontal) reduces our problem greatly to few variables which will allow us to simply solve for a. F(due to gravity pulling on B) + F(fraction working against the force of B) = ma 10(3 + 5) - 0.14(15)(10) = (15 + 8)a 10(8) - 21 = 23a 59 = 23a a = 2.56 Which matches up with the answer key. I can find the tension on my own, I just want to know if I'm understanding the underlying process correctly. Thank you.