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What is the speed of recoil of the chair and cat?

  1. Apr 3, 2013 #1
    1. The problem statement, all variables and given/known data
    A cat crouches on the floor at a distance of 1.7 m from a desk chair of height 0.45 m. The cat jumps onto the chair , landing with zero vertical velocity. The desk chair has coasters and rolls soomthly away when the cat lands. The cats mass is 6.4 kg , the chairs mass is 12 kg. what is the speed of recoil of the chair and cat?





    3. The attempt at a solution
    1/2gt^2=0.45m
    t=0.303s
    1.7/0.303=5.61ms horizontal velocity component
    5.61*6.4=12v
    v=2.99m/s
     
  2. jcsd
  3. Apr 3, 2013 #2

    Doc Al

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    Staff: Mentor

    So far, so good.

    After the "collision" the chair and cat move as one body.
     
  4. Apr 3, 2013 #3
    so would it be 5.61*6.4=(12+6.4)v?
     
  5. Apr 3, 2013 #4

    Doc Al

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    Staff: Mentor

    That's correct.
     
  6. Apr 3, 2013 #5
    thank you!
    was that center of mass equation used or was that m1v11=m2v1?
     
  7. Apr 3, 2013 #6

    Doc Al

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    Staff: Mentor

    That was conservation of momentum applied to an inelastic collision.

    m1v1 + m2v2 = (m1 + m2)vf

    (Here, v2 = 0, since the chair was initially at rest.)
     
  8. Apr 3, 2013 #7
    I see now,
    thank you very much!
     
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