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Homework Help: Cart moving with a spring.

  1. Jul 22, 2012 #1
    1. The problem statement, all variables and given/known data
    A 2kg cart has a spring with k=5000N/m attached to its
    front parallel to the ground. This cart rolls at 4m/s toward a stationary
    1kg cart.
    What is the maximum compression of the spring during the collision
    3. The attempt at a solution
    I think the spring will stop compressing when the 2 carts are moving
    at the same speed. And there will be a point where the potential energy in the spring
    plus the KE of the 2 carts will equal the original energy of moving cart.
    so I think I should start with
    [itex] kx^2+m_2v^2+m_1v^2=m_2{v_0}^2 [/itex]
    now I need another equation because I have 2 unknowns in my one equation
  2. jcsd
  3. Jul 22, 2012 #2

    Doc Al

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    Staff: Mentor

    What else is conserved in every collision?
  4. Jul 22, 2012 #3
    ok thanks momentum. ok i got it figured out.
  5. Jul 22, 2012 #4
    what an interesting question..

    The presence of a spring tells you that the collision will be elastic.

    What can you say about the center of mass of the system in an elastic collision?
  6. Jul 22, 2012 #5
    I didnt think this one through very much, but will the center of mass stay the same.
  7. Jul 22, 2012 #6


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    Homework Helper
    Gold Member
    2017 Award

    A hint for answering the question about the motion of the center of mass: The total momentum of a system of particles is equal to the total mass of the system times the velocity of the center of mass.
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