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Homework Help: Bullet shot into pendulum - conservation of energy

  1. Oct 13, 2008 #1
    1. The problem statement, all variables and given/known data
    A 27-g rifle bullet traveling 230m/s buries itself in a 3.3-kg pendulum hanging on a 2.9-m-long string, which makes the pendulum swing upward in an arc.
    Determine the vertical and horizontal components of the pendulum's maximum displacement.
    x=? and h=?

    2. Relevant equations
    v= (m+M)/m * sqr root (2gh)

    3. The attempt at a solution
    I just expanded on the above equation and derived several others ..dont know where to go next.. L = length of string ; M=block's mass ; h=max height ; x=distance on x axis ; m=bullet's mass
    v= (m+M)/m * sqr root (2gh)
    (v* (m/m+M)^2)/(2g)=h
    h= L(1-cos theta)
    cos-1 theta(-1 ((h/L)-1) = theta
    L sin theta = x
    EDIT: sorry nicksauce. I have now included the question.
    Last edited: Oct 13, 2008
  2. jcsd
  3. Oct 13, 2008 #2


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    Homework Helper

    Re: pendelum

    What exactly is the question here? I see no question marks in your post.
  4. Oct 14, 2008 #3


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    Re: pendelum

    I would be inclined to use "conservation of Energy". You can calculate the kinetic energy of the bullet and you can take the potential energy to be 0 at the bottom of the arc. At the highest point the kinetic energy of both is 0 so all energy has be changed to potential energy. From the potential energy you can find the height.

    I think this will get a better response in the physics section so I am going to move it there.
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