# Angular Impulse, finding the angle of action?

1. Dec 7, 2008

### Phan

1. The problem statement, all variables and given/known data
A cue hits the billiard ball at the position shown. The collision lasts 90 ms with an
average force of 420 N. If R = 7 cm, m = 300g, k = 0.1.
(ignore friction during impact)
*Didn't post the rest since they are irrelevant.

2. Relevant equations
J(angular) = (x*F*t)/I
J(linear) = (F*t)/m

3. The attempt at a solution
I know how to figure out everything else after the impulse force (since you just solve for time using the two angular and linear equations), but I'm still stuck on the idea of angular impulse. I know that it works like Torque (r*F) and that you have to either use the moment arm angle or sine of the smallest angle, but I'm not sure which angle that is on the diagram @_@

Is it the one that I have labelled? If so, I'm feeling stupid here, but I can't figure out how to get that angle. Any help would be greatly appreciated :)

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