What is the angular acceleration at a given point during rotation?

[eestep]

Homework Statement

A disk with a radius of .27 meters is originally at rest. It then starts to spin under a constant angular acceleration. After 2 rotations, magnitude of total acceleration (considering both centripetal and tangential acceleration) is 52 m/s². What is angular acceleration in rad/s² at this point?
R=.27

Homework Equations

a=R$$\sqrt{}\alpha^2+\omega^4$$

The Attempt at a Solution

$$\Delta\theta$$=2(2$$\pi$$)=4$$\pi$$

 

[jbsteele]

\alpha=\frac{\Delta\omega}{\Delta t}=\frac{4\pi}{2}=2\pia=R\sqrt{}\alpha^2+\omega^452=.27\sqrt{}\alpha^2+\omega^4(\alpha^2)=\frac{52-.27\omega^4}{.27}\alpha=\sqrt{\frac{52-.27\omega^4}{.27}}