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Homework Help: 2 blocks being pushed apart by a spring

  1. Oct 21, 2009 #1
    1. The problem statement, all variables and given/known data

    A light spring with k=3.85 N/m and x = 8.00cm is held between a 0.250kg block on the left and a 0.500kg block on the right. The spring exerts a force on each block tending to push them apart. The blocks are simultaneously released from rest. Find the acceleration with which each block starts to move given that the coefficient of kinetic friction between each block and the surface is
    a) 0
    b) 0.100
    c) 0.462

    2. Relevant equations

    Well we know that the sum of the forces = ma
    F of exerted by the spring = -kx

    3. The attempt at a solution

    so i figured out the magnitued of the force of the spring to be 0.308N

    what i am not to sure of is, what portion of the force is applied to each block. I attempted to solve the problem if each block gets half of the force. But when i get to part b, my calculations show

    F - F(friction) = ma --> 0.154 - (0.250(9.8)(0.1))=0.250a however this works out so that the Force(friction) is larger than the applied force. I was expecting this for part c but not part b. This leads me to believe that the force applied on each block is not just half of the total force.

    Any help would be greatly appreciated.


  2. jcsd
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