Here's a pulley problem that has got me stopped; I'd appreciate any help that's offered.(adsbygoogle = window.adsbygoogle || []).push({});

There are two blocks, A (44 N) and B (22 N) connected via a rope that stretches over a pulley. Block A is resting on a table, and block B is hanging over the edge. Block C is positioned on top of Block A.

The question reads: "Given that the coefficient of static friction between Block A and the tabel is 0.20, what is the minimum weight of Block C to keep Block A from sliding off the table?"

(The answer that is given is 66 N, but I can't seem to get this)

I tried starting off with:

Block A=M=44N Block B=m=22N

(let F stand for the friction force)

T-F=Ma and mg-T=ma

Solving for Tension and setting them equal gives:

mg-ma=F+Ma

Rearranging some more and solving for a gives:

a= (mg-F)/(m + M)

The Tension on Block A then becomes M(mg-F)/(m + M) = 8.8 N

So then in order for Block A to resist motion, the Friction between it and the table must be equal to T, so F=T=8.8 .20 * (4.489 + C) * 9.8 = 8.8 but then the mass of C ends up being zero. Where did I go wrong?

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# Homework Help: Pulley Problem - Please give me hand here!

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