Homework Help: Ballistic cylinder

1. Nov 27, 2005

Punchlinegirl

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
$$(MR^2) \omega = (MR^2 + (1/2)MR^2) \omega$$
(.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. Nov 27, 2005

stuplato

Conservation of momentum (mv = (M+m)v') will get a linear speed, which can be converted to rotational speed if I am remembering right...

3. Nov 27, 2005

stuplato

You lost a square on the .09 on the left side...

4. Nov 27, 2005

lightgrav

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
5. Nov 28, 2005

Punchlinegirl

Can you explain to me how you got the .5 for the initial L?

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook