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3 blocks with friction

  1. Feb 11, 2008 #1
    1. The problem statement, all variables and given/known data
    There are three blocks on a table. They are connected by a massless cord and pulled to the right. From rigt to left, it follows: T3, block 3, T2, block 2, T1, block 1
    m1: 2.5kg
    m2: 9.5kg
    m3: 1.5kg
    mu kinetic: .051
    The pulling force is equal to T_3 = 98.0 N. What is the tension T_2?
    2. Relevant equations
    I think my equations may be incorrect, but here goes
    F[tex]_{}fr[/tex]=F[tex]_{}N[/tex] + [tex]\mu_{}k[/tex]
    F[tex]_{}pull[/tex]=F[tex]_{}fr[/tex] + ma

    3. The attempt at a solution

    I solved for accel. and then plugged it into the equation for tension and I got a value of 81.11 N, but that is not correct.

    Any help please?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 11, 2008 #2


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    Science Advisor
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    Gold Member

    The friction force is not correct. For objects in motion, it's [tex] F_{friction} = \mu_k(N)[/tex], where N is the normal force between the block and table. You're going to have to calculate it for each block, then use Newton 2 and 'free body diagrams'. Are you familiar with them?
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