I am having quite a time with this problem, I would appreciate any assistance.(adsbygoogle = window.adsbygoogle || []).push({});

Block B, of massmB, rests on block A, of massmA, which in turn is on a horizontal table top . The coefficient of kinetic friction between block A and the table top isuKand the coefficient of static friction between block A and block B isuS. A light string attached to block A passes over a frictionless, massless pulley and block C is suspended from the other end of the string.

The Q is… What is the largest massmCthat block C can have so that blocks A and B still slide together when the system is released from rest?

My assumption is we want acceleration to be at the maximum that keeps block B over A. The larger the mC, I am assuming the larger the a. (I don’t know how to express that thought mathematically, if it is right)

This is what I did.

A: T-uK*(mA+mB)=mA*a

B: fs=uS*mB*g=mB*a…..fs=uS*g=a

C: mC-T=mC*a

FA-FB=T , I plug eq.A into FA, eq.B into FB, and solve for T in eq.3 to isolate the mC.

My answer for mC, which I know is wrong was...uk*(mA+mB)-us*mB

I am so confused. I have been struggling with this problem all day. I separated into components numerous times. (I don’t think that’s where my problem lays)

Someone plx help me to understand why I don’t understand.

Thanks

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# Homework Help: 3 masses, 1 pully

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