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Ballistic pendulum

  1. Mar 7, 2008 #1
    1. The problem statement, all variables and given/known data
    a ballistic pendulum is hit by a bullet traveling 500m/s , the ballistic pendulum is a block of wood hanging from a string.
    the block of wood (1kg) is hanging from the string of 2.5m
    the bullet has mass .006kg @ 500m/s
    the bullet passes right through the block of wood before it makes any significant movement.
    the block of wood swings to a max angle of 12 degrees with the vertical.

    ive drawn out a microsoft paint image.
    http://img512.imageshack.us/img512/262/bulletib5.jpg [Broken]

    2. Relevant equations
    conservation of energy
    and momentum

    3. The attempt at a solution

    here is my solution
    please tell me if i got the correct answer, this is from a test i took yesterday

    http://img246.imageshack.us/img246/5002/bullet2lv3.jpg [Broken]

    edit : ive made changes,, the correct initial velocity of the block .98 m/s
    and the bullets initial momentum is 3 kg-m/s
    and the final bullet velocity is 333.333,, is this correct?
    thank you
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Mar 7, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    I assume the problem is to find the speed of the bullet after it passes through the block.

    No, it's not correct.

    (1) Recalculate a more accurate value for the change in height of the block.

    (2) Recalculate the initial (post bullet) velocity of the block.

    (3) Recalculate the initial momentum of the bullet. (It's not 6 kg-m/s.)
  4. Mar 7, 2008 #3
    I see i made the mistake, the velocity of the block initially should be .98 m/s NOT 3.13

    ic the wrong bullet momen. now, it is 3

    so should the final velocity of the bullet be 333.3333 m/s?

    or is it 327, ?
    thank you
    Last edited: Mar 7, 2008
  5. Mar 7, 2008 #4

    Doc Al

    User Avatar

    Staff: Mentor

    I get a slightly different value for the velocity.


    That's close to what I get.

    That's even better. :approve:
  6. Mar 7, 2008 #5
    i wrote 333.333 on the test
    now i dont know what to say, whether it got it wrong or not
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