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Homework Help: Help: Impulse

  1. Oct 26, 2004 #1
    A bullet of mass 0.11 kg and moving along the horizontal direction with a speed 1129.8 meters/sec hits a wooden block of mass 12.7 kg and gets embedded in it. Find the impulse acting on the block in meters/sec.

    Here's what I did:
    initial momentum = (0.11*1129.8) + (12.7*0) = 124.278
    final momentum = (0.11 + 12.7) v

    inelastic collision, momentum is conserved; so:
    initial momentum = final momentum
    124.278 = 12.81v
    v = 9.702 m/s
    final momentum = (12.81*9.702) = 124.278

    Impulse = final momentum - initial momentum
    = (124.278-124.278)
    = 0

    The answer is 123.21 meter/sec. What did I do wrong? Please help. Thanks!
  2. jcsd
  3. Oct 26, 2004 #2
    Sorry, supposed to be :The change of the bullet's velocity is due to the impulse force exerted on the bullet by the block.
    The change of the block's velocity is due to the impulse force exerted on the block by the bullet.
    Last edited: Oct 26, 2004
  4. Oct 26, 2004 #3
    Thanks Leong!
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