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Conservation Force and Springs

  1. Nov 15, 2011 #1
    1. The problem statement, all variables and given/known data
    A block is on a frictionless incline. A block at the bottom of the incline is resting up the incline against a spring. The first block is released. The blocks stick and compress the spring. What is the common velocity immediately after collision?


    2. Relevant equations

    Kinetic energy of the two blocks + potential energy of blocks = potential energy of spring

    3. The attempt at a solution

    I am not concerned with solving this equation for the velocity. I am just concerned with understanding how to get to this equation. My exam useful equations study sheet shows that kinetic initial+ potential initial = kinetic final + potential final.
     
    Last edited: Nov 15, 2011
  2. jcsd
  3. Nov 15, 2011 #2
    Is the kinetic final cancelled out because velocity would be zero at the final state?
     
  4. Nov 16, 2011 #3

    Doc Al

    User Avatar

    Staff: Mentor

    That equation applies when mechanical energy is conserved. (Which is not the case during the collision of the two blocks.)

    In the final position, the blocks are at rest. So their kinetic energy is zero.
     
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