# Stupid Question

by Cyrus
Tags: stupid
 P: 4,778 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.
 P: 255 Well to me the free-body diagrams look right for sure and the reasoning looks good as well. Your net forces a fine and i they would have the same acceleration. I know it's probably not reassuring to have me say it looks fine, but I'm saying it anyway : )
 P: 4,778 Does anyone else agree, no offense big man? Just makin sure.
P: 15,294

## Stupid Question

Surely, there's a trick to this question.

Unless it is a given that the pond is frozen, the masses will not sit on the surface.
 P: 4,778 HAAHAHAHAHAH, i forgot to type frozen......sorry.
 P: 15,294 Ah. Then never mind. Carry on.
 P: 4,778 Does it look correct though? Theres another problem in his book that is worded funny, and I keep getting a different anwser than what they have. Ill post that problem up too, maybe you can find something im not seeing.

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