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Homework Help: Conservation of energy minimum speed

  1. Feb 10, 2013 #1
    1. The problem statement, all variables and given/known data
    Gus is at end of rope. He needs to reach roof. His friend fires cannon ball horizontally hitting Gus and get stuck in belt. Find minimum speed of cannon ball for Gus to reach roof. 50m is rope. 99kg is Gus. 1kg is ball. 45° angle in diagram

    2. Relevant equations
    conservation of energy
    Et1 = Et2
    1/2mv^2 = mgh
    p = mv

    3. The attempt at a solution
    1/2(1)v^2 = 99(9.8)(50xsin45°)
    1/2v^2 = 34301.75
    v = 260 m/s
    is this right?

    Attached Files:

    Last edited: Feb 10, 2013
  2. jcsd
  3. Feb 10, 2013 #2
    conservation of energy:
    1/2 (m+M) V² = (m+M)gh
    V² = 2gh
    conservation of momentum:
    mv = (m+M)V
    v = (m+M) sqrt(2gh) / m
    is this correct?
  4. Feb 10, 2013 #3
  5. Feb 10, 2013 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Looks good. The collision of cannonball and person is treated as an inelastic collision.
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