How Does Angular Momentum Affect Projectile and Rod System Post-Collision?

[jessedevin]

Homework Statement

A projectile of mass m moves to the right with a speed vi. The projectile strikes and sticks to the end of a stationary rod of mass M, of length d, that is pivoted about a frictionless axle through its center.

(a) Find the angular speed of the system right after the collision. (Use v_i for vi, m, M, and d as appropriate in your equation.)
(b) Determine the fractional loss in mechanical energy due to the collision. (Use v_i for vi, m, M, and d as appropriate in your equation.)

Homework Equations

I_f$$\omega$$_f=I_i$$\omega$$_i
W= K₁-K₂

The Attempt at a Solution

http://qaboard.cramster.com/Answer-Board/Image/2007111219463329548144409250092.jpg
i did it like this but for some reason my part (b) is saying that I'm wrong. Can someone help?

 

[borgwal]

It all looks fine, but question (b) asks about the *fractional* energy loss, so you should divide your final answer by mv^2/2.