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## Homework Statement

I need to find the average acceleration of a gramophone record.

Initial angular velocity, W = 0

Final angular velocity, w = 3.50rad s^-1

angular displacement, 8 = 0.25rad

## Homework Equations

The equation given by the answer is

t= 8/w

a = ( w - W ) / t

the answer is 49.0 rad s

^{-2}

## The Attempt at a Solution

This is the equation I use

w

^{2}= W

^{2}+ 2a8

and I get 24.5rad s

^{-2}

But if I multiply it with 2, the angular acceleration will become 49rad s

^{-2}

That mean my equation will become

w

^{2}= W

^{2}+ a8

Can anyone explain this to me?

Or I use a wrong equation?