Laser experiment, determine angular velocity

[Gauss M.D.]

Homework Statement

A circular cannister of some reflective liquid is spinning at some ω. The distance between the cannister and the surface is given by

h(r) = h(0) + (ω²/2g)r²

Where g ≈ 9.82 and r is the distance to the axis of revolution. When we shine two parallell laser beams on the surface, we find that they meet at a point 22 cm above the surface.

Find ω.

Homework Equations

f = R/2

The Attempt at a Solution

We have a parabolic mirror with radius of curvature = 0.44 m. But I'm not really sure how to find the equation for a parabola given the curvature. I was well on my way to taking the gradient of the parabola and setting up some kind of system of vector equations, but I suspect that would be overkill...

 

[Gauss M.D.]

Figured it out.