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Momentum problem please help

  1. Feb 19, 2006 #1
    hey guys. heres the problem:

    heres what i tried:

    p(bullet)=mv
    p= 8 (initially)

    p(bullet)=mv
    = 4 (after impact)

    the bullet exerted a momentum of 4 onto the cart.

    p(cart)= mv
    4= 200v
    v=.02m/s after getting shot at by one bullet

    19/.02= 950 bullets that need to be fired in order for the car to move at 19m/s

    950 bullets/20= 47.5 bullets per second

    however, this is wrong
     
  2. jcsd
  3. Feb 19, 2006 #2

    lightgrav

    User Avatar
    Homework Helper

    Momentum is a VECTOR quantity.
    the direction after bouncing off the cart is negative,
    so the momentum transferred from one bullet to cart is 12 Ns.
    (momentum is conserved, so it is transferred, not exerted).
     
  4. Feb 19, 2006 #3
    thank you :!!)
     
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