Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Ballistic cylinder

  1. Mar 29, 2010 #1
    1. The problem statement, all variables and given/known data

    A 13.0 g bullet is fired at 578.1 m/s into a solid cylinder of mass 24.1 kg and a radius 0.11 m. The cylinder is initially at rest and is mounted on 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 2.20 cm from the center. Find the angular velocity of the system after the bullet strikes and adheres to the surface of the cylinder.

    2. Relevant equations

    conservation of angular momentum

    3. The attempt at a solution

    I tried,

    .013 x (.022^2) (578.1/.11) = ((.013)(.022^2) + (.5)(24.1)(.11^2)) x W

    I got .227rad/s as an answer but that was incorrect. Any ideas?
     
  2. jcsd
  3. Mar 30, 2010 #2

    Filip Larsen

    User Avatar
    Gold Member

    If you think of the bullet as an impulsive force on the cylinder you should be able to figure out how much of that force is radial to the cylinder (which is absorbed by the bearing) and how much is tangential (which will make the cylinder rotate). If I do the calculation I end up with a angular speed of around 1.13 rad/s.

    The right-hand side of your equation looks ok to me, but I'm not sure I understand how you arrived at the left-hand side of your equation. I get something similar but not quite the same. Perhaps you missed taking only the tangential part of the impulse.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook