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Homework Help: Ballistic Pendulum Rifle

  1. Nov 4, 2008 #1
    The problem:

    https://tycho-s.phys.washington.edu/cgi/courses/shell/common/showme.pl?courses/phys121/autumn08/homework/06/IE_algebra_ballistic_pendulum_MOM/pic.gif [Broken]

    A rifle bullet of mass m = 0.03 kg traveling at vb = 240 m/s collides with and embeds itself in a pendulum of mass M = 2.88 kg, initially at rest and suspended vertically by massless strings of length L = 2 m.

    How high does the pendulum-bullet combination rise after the collision?

    I don't know the process for solving this equation, so help would be appreciated.
     
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Nov 4, 2008 #2

    Borek

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    Energy preservation. Kinetic gets converted into potential.
     
  4. Nov 4, 2008 #3
    Okay, so I need to use PE = mgh. I don't understand what I do with the velocity of the bullet and how to setup the problem, if I could get a little more guidance it would help me out

    Thanks.
     
  5. Nov 4, 2008 #4

    Borek

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    What is formula for kinetic energy?
     
  6. Nov 4, 2008 #5
    We did this the other day, except we just manipulated the formulas instead of working with actual values.
    I am going to attempt to make sense of what I have for that note, so you may hear from me soon...
     
  7. Nov 4, 2008 #6
    KE = (1/2)mv2
     
  8. Nov 4, 2008 #7

    Borek

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    Is there something you still don't know? Just beware which mass is which - ballistic pendulum mass after hit is that of pendulum PLUS bullet.
     
  9. Nov 4, 2008 #8
    I don't understand what it is I do with the equation for Kinetic Energy, I'm supposed to find the height of the bullet-pendulum system after the bullet hits the pendulum.
     
  10. Nov 4, 2008 #9

    Borek

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    h as of mgh.
     
  11. Nov 4, 2008 #10

    Doc Al

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    This problem is best solved in two stages:
    (1) The collision itself. You need to find the speed of the block+bullet immediately after the collision. Hint: Energy is not conserved, but something else is.
    (2) The rising of the pendulum after the collision. Here you do use energy conservation, as Borek explains.
     
  12. Nov 4, 2008 #11

    Borek

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    Do we have an emoticon for selffishslapping? :blushing:
     
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