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Homework Help: Elastic collision question: two marbles

  1. Oct 3, 2007 #1
    I just want to know if I am approaching this question correctly.

    1. The problem statement, all variables and given/known data

    Two marble spheres of masses 30 and 20 grams, respectively, are suspended from the ceiling by massless strings (.95m long). The lighter sphere is pulled aside through an angle of 75 degrees and let go. It swings and collides elastically with the other sphere at the bottom of the swing.
    a) To what maximum angle will the heavier sphere swing.
    b) To what maximum angle will the lighter sphere swing.

    2. Relevant equations
    Conservation of mechanical energy
    Conservation of momentum
    Conservation of kinetic energy

    3. The attempt at a solution

    1. Calculate the height the small sphere is above the "rest" state. Use this height and conservation of mechanical energy to get the velocity.
    2. Use conservation of momentum and conservation of kinetic energy to get the velocity of the larger and smaller spheres after the collision.
    3. Use conservation of mechanical energy to get the new heights of the large and small sphere.
    4. use trig to get the angles of each sphere.

    Does that approach make sense?

  2. jcsd
  3. Oct 3, 2007 #2


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