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Springs, Masses, and Friction oh mY!

  1. Mar 20, 2007 #1
    1. The problem statement, all variables and given/known data

    A block with mass M = 5.5 kg rests on a frictionless table and is attached by a horizontal spring (k = 1.5E2 N/m) to a wall. A second block, of mass m = 1.32 kg, rests on top of M. The coefficient of static friction between the two blocks is 0.36. What is the maximum possible amplitude of oscillation such that m will not slip off M?

    2. Relevant equations

    F_friction=(coeff friction)(normal force)=u*F_n

    3. The attempt at a solution

    So for the block to slide the force of friction must be equal too/less than the force imparted from the spring accelerating the blocks.

    The F_accel must equal the spring force at the peak (accel will be highest then)
    F_a=F_spring=kx, where we can find the value of F_a, but we don't know the values of k or x.

    I tried applying some engery type eqns like E=0.5kA^2 or E=KE+PE but we don't know any amplitudes, velocities, etc.

    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 21, 2007 #2
    See, youre given k and youre given the coeff of friction and the masses. So you can find the frictional force. This must be equal to the spring force as you said (max displacement). From there you can find x, which is your amplitude.
  4. Mar 21, 2007 #3
    Wow, forgot I was given "k". Don't have time now but will look at it later.

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