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## Homework Statement

A grindstone, initially at rest, is given a constant angular acceleration so that it makes 20.0 rev in the first 8.00 s. What is its angular acceleration?

(a) 0.313 rad/s2 (c) 2.50 rad/s2 (e) 3.93 rad/s2

(b) 0.625 rad/s2 (d) 1.97 rad/s2

## Homework Equations

Rotational Kinematic equations

## The Attempt at a Solution

Ok so I am using the equation ω = ω (initial) + ∝ T

BUT my answer is the wrong one. It seems that I have to use this equation ω^2 = ω (initial) ^2 + 2∝Θ

but what do I put in liew of "Θ"?

I just don't understand why is that I have to use that equation?