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!!