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Vertical spring physics

  1. May 10, 2008 #1
    An 5 kg block is fastened to the top of a vertical spring (perpendicular to the floor) with a spring constant of 1000 N/m. A 3 kg block sits on top of the 5 kg block.

    The springs are pushed down so that they oscillate.

    I need help finding the magnitude of the maximum acceleration the blocks can obtain while still remaining in contact. I have no idea where to begin.

    Any suggestions!? Help please!
     
  2. jcsd
  3. May 10, 2008 #2

    Hootenanny

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    HINT: Consider the forces acting on the 3kg block, which force will be zero when the blocks lose contact?
     
  4. May 10, 2008 #3
    Ok so when the blocks lose contact, the force of the spring-mass will be equal to the force of gravity on the 3 kg block.

    M(3)*a=-2mg, is this correct?
     
  5. May 10, 2008 #4

    Hootenanny

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    You've still not answered my first question. What are the forces acting on the top block?
     
    Last edited: May 10, 2008
  6. May 10, 2008 #5
    The forces acting on the block are gravity and the force of the spring, correct? Or friction??
     
  7. May 10, 2008 #6

    Hootenanny

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    Correct, but what I was trying to get at is that the force of the spring acts through the normal force exerted on the block. Hence, the net force acting on the block is [itex]N - mg[/itex]. Can you now use this information to write an equation using Newton's second law?
     
  8. May 11, 2008 #7
    ma = N - mg

    but what is the magnitude of the normal force !?!?!? kx !?
     
  9. May 13, 2008 #8

    Hootenanny

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    Correct! And what do you know about the normal force when the block leaves the surface of the 5kg block?
     
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