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Momentum of a Bullet Contacting a Block

  1. Oct 25, 2011 #1
    1. The problem statement, all variables and given/known data
    A bullet with a mass of 4.0 g and a speed of 650 m/s is fired at a block of wood with a mass of 0.095 kg. The block rests on a frictionless surface, and is thin enough that the bullet passes completely through it. Immediately after the bullet exits the block, the speed of the block is 23 m/s.

    (a) What is the speed of the bullet when it exits the block?

    (b) Is energy conserved in this collision? (yes or no)

    2. Relevant equations

    3. The attempt at a solution


    v1≈650.00 (Apparently this is wrong.)
    Last edited: Oct 25, 2011
  2. jcsd
  3. Oct 25, 2011 #2


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    Your mass units need attention.
  4. Oct 25, 2011 #3
    I don't see any mass unit that needs attention. The only thing I did with mass was convert m1 (4.0 g) to the SI unit kg.
  5. Oct 25, 2011 #4


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    4g is not 4000kg. :smile:
  6. Oct 25, 2011 #5
    Aww crap! Dang, I feel so ridiculous for reversing it up!
  7. Oct 25, 2011 #6


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    We all have our moments. That would be some big bullet. No wonder it didn't slow down.
  8. Oct 25, 2011 #7
    With the correct unit conversions and your same formula, I got 296.94
  9. Oct 25, 2011 #8
    I got 103.75. :confused:
  10. Oct 25, 2011 #9
    MV+MV = MV+MV
    .004kg*650m/s + .095kg*0 = .004kg*VF + .095kg*23
    2.6 = .004*VF + 2.185
    .0415 = .004VF
    Vf= 103.75

    0.0 my bad, man sorry about that
  11. Oct 25, 2011 #10
    No problem! Thanks for confirming!
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