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Homework Help Forum: Physics

Posted by Annie on Saturday, October 31, 2009 at 2:02pm.

A block of mass m1 = 4.80 kg sits on top of a second block of mass m2 = 15.6 kg, which in turn is on a horizontal table. The coefficients of friction between the two blocks are µs = 0.300 and µk = 0.100. The coefficients of friction between the lower block and the rough table are µs = 0.500 and µk = 0.400. You apply a constant horizontal force to the lower block, just large enough to make this block start sliding out from between the upper block and the table.


Determine the magnitude force needed to initiate this motion.


Determine the acceleration you measure for each block in this situation

  • Physics - bobpursley, Saturday, October 31, 2009 at 2:19pm

    First, find the force between the blocks.
    m1*g*mus
    That force will produce an accelearation on the upper block of a=F/m=g*mus
    but to get that acceleartion, on has to apply a force to the lower block..
    F=totalmass*a= (m1+m2)*g*mus
    that answers the first question.

    Now, the acceleration for each block
    block 1: a=m1*g*mu<k>/m1
    for block2: net force actin on lower block is pushing force- force on block1, or
    (m1+m2)*g*mus - m1*g*muk
    and acceleration of the lower block is that divided by m2.

    check my thinking.

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