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Homework Help: Spring Problem

  1. Dec 11, 2004 #1
    A block of mass m is attached to a horizontal spring with constant k. resting on top of this block is another block of mass m. a coefficient of static friction mu exists between the two blocks. now suppose the spring is initially at equilibrium length, and someone gives it a push. the block moves in SHM in response. At a certain distance from equilibrium, the top block starts wo slide off the bottom one, find the x in terms of the given quantities and g.

    So with the the moment when the top block slides off the block is when umg=ma? and where do I go from here?
     
  2. jcsd
  3. Dec 11, 2004 #2
    [tex]
    \mu mg = kx
    [/tex]

    The spring force = the frictional force.
     
  4. Dec 11, 2004 #3

    Doc Al

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    Staff: Mentor

    Right. So this tells you the maximum acceleration that the top block can withstand before it starts sliding. So find the acceleration of the system as a function of distance from the equilibrium postion. (You know the force on the system from the spring, and you know the mass of the system.)
     
  5. Dec 11, 2004 #4
    Hey futb0l,

    Are you sure about that? I could be wrong but for the top block [tex]ma <_= \mu m g [/tex] (couldn't figure out less than or equal sign) . So when it isn't slipping [tex] kx = 2ma [/tex]
     
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