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Velocity question? Need help

  1. Jun 22, 2004 #1
    Velocity question?? Need help..

    An 80.0 kg man is standing on a frictionless ice surface when he throws a 4.00 kg book at 20.0 m/s. WIth what velocity does the man move across the ice?


    Would I be using Mass= weight/gravity?

    Astronaut weight = 80.0 kg
    Astronaut v = ? m/s

    Book weight= 4.00 kg
    Book v= 20.0 m/s
     
  2. jcsd
  3. Jun 22, 2004 #2

    chroot

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    Are you familiar with the conservation of linear momentum?

    - Warren
     
  4. Jun 23, 2004 #3
    Apply the law of linear momentum.
    Before the throw: Man mass = 80kg, velocity = 0, Book mass = 4kg, velocity = 0.
    After the throw: Man mass = 80kg, velocity = V. Book mass = 4kg, velocity = 20.

    M1U1 + M2U2 = M1V1 + M2V2
    (80x0) + (4x0) = (80V) + (4x20)
    0=80V + 80
    80V = -80
    V = -80/80
    V= -1m/s.
     
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