This is a GRE question, but it's so basic I thought I'd just put it here. Here it is with the solution:(adsbygoogle = window.adsbygoogle || []).push({});

http://grephysics.net/ans/9277/6 The answer is "D" by the way.

So my problem is with the way the weight of the block is distributed.

I get that each triangular block only "feels" half of the square block, so M/2 of mass. But then they assume that's the horizontal force via some weird trig that seems pointless (I can't figure out where they get a square-root 2 from).

My understanding was that you get half of the block's weight pushing down on the triangular block, and half pushing it horizontally. So you'd have g*M/4 pushing straight down and (m+M/2)*g*u pushing horizontally, for each block.

Why am I wrong?

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# Homework Help: Friction and moving blocks on inclines

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