(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 500-N concrete block is to be lifted by the pair of tongs shown. Determine the smallest allowable value of the coefficient of static friction between the block and the tongs at F and G.

See Diagram: [PLAIN]http://img192.imageshack.us/img192/1315/sprob826.jpg [Broken]

2. Relevant equations

Fm=[tex]\mu[/tex]sN

[tex]\Sigma[/tex]F=0

[tex]\Sigma[/tex]M=0

3. The attempt at a solution

Well,

deframing everything

[tex]\Sigma[/tex]Fy=0, so 500N+Ay+By=0

[tex]\Sigma[/tex]Fx=0, Ax+Bx=0

Then I take the moments about A and B in the frame AB and I get Ay = 250 and By =250 . Then I say, Ff=250=[tex]\mu[/tex]Nf. Nf= 250/[tex]\mu[/tex].

Then I take the moment about one of the frames because they're symmetrical. So [tex]\Sigma[/tex]Ma=0,(250)(.180)-(Nf)(.540)=0. Then I get Nf=83.33, so then [tex]\mu[/tex]s= 250/83.33 = 3. But the thing is, that isn't the answer. I have the answer only but I can't seem to arrive at it. What am I doing wrong?

Thanks!!

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# Statics: Friction Problem

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