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Homework Help: Ballistic cylinder

  1. Nov 27, 2005 #1
    A 14.0 g bulllet is fired at 396.1 m/s into a solid cylinder of mass 18.1 kg and a radius 0.45 m. The cylinder is initially at rest and is mounted on a fixed vertical axis that runs through it's center of mass. The line of motion of the bullet is perpendicular to the axle and at a distance 9.00 cm from the center. Find the angular velocity of the system after the bullet strikes and adheres to the surface of the cylinder.
    First I converted the velocity to angular velocity by dividing by the radius.
    I used conservation of angular momentum
    [tex] (MR^2) \omega = (MR^2 + (1/2)MR^2) \omega [/tex]
    (.14)(.09)(880.2) =((.14)(.09^2) + (1/2)(18.1)(.45^2)) \omega [/tex]
    Solving for omega gave me .545 which wasn't right.. can someone tell me what I'm doing wrong? Thanks
  2. jcsd
  3. Nov 27, 2005 #2
    Conservation of momentum (mv = (M+m)v') will get a linear speed, which can be converted to rotational speed if I am remembering right...:rolleyes:
  4. Nov 27, 2005 #3
    You lost a square on the .09 on the left side...
  5. Nov 27, 2005 #4


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    initial L should be .5 [m.kg.m/s] , (easiest by r x p) ... your omega_i is off.
    Also, 14 gram = 0.014 kg .
    Last edited: Nov 27, 2005
  6. Nov 28, 2005 #5
    Can you explain to me how you got the .5 for the initial L?
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