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Need help for question about spring oscillation

  1. May 2, 2016 #1
    1. The problem statement, all variables and given/known data
    I want to know why the answer is C not B. Thanks.

    2. Relevant equations
    F=kx

    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. May 2, 2016 #2
    1. the force will be -kx , as spring opposes the displacement
    draw the force diagram on the block and see what is the net force on the block-ask yourself can it support oscillations of the block or not ?
     
  4. May 4, 2016 #3
    @drvrm Thanks.
     
  5. May 4, 2016 #4
    but you should give complete argument;
    1. initially a displacement say y in the vertical direction will lead to two forces- compression of upper spring will give -ky down ward and extension of lower one will give -ky down ward, as there is significant friction F(friction) will oppose the motion of the mass -pointing up if movement is downward-
    after reaching the rest position the energy of the mass will move further down and spring forces will point up but the friction will oppose the motion . so a cycle of oscillation can not be sustained mainly due to energy dissipation .
     
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