My friends a pre-med student and hes taking basic phyiscs 1. He asked me to do two problems. Can you double check to make sure I did not tell him the wrong thing! Problem 1.) There are two square masses, side by side on a frictionless pond. Mass A is 150kg, and mass b, is 50kg. A force of 100N is applied at mass A, find the reaction force that mass B exerts on mass A. So I said on block A: simga(F): (150)a = 100N - F and on block B: sigma(F): F = 50a since both blocks are in contact, they have to have the same acceleration, so both a's are equal. so that means a = F/50, and I plug that into block A's equation. 150(F/50) = 100 -F and so F = 25 N Does that sound right? I did not have a solution to check for a mistake. And i feel stupid asking this question, but his test is comming up and I dont want him to fail because of what I told him. I was real stupid the first time I did it because I approached it as a statics problem without thinking, I just said oh, its 100N.........errrrrr whoops......... that was dumb of me.