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## Homework Statement

A mass attached to a 48.9 cm long string starts from rest and is rotated 31 times in 78.0 s before reaching a final angular speed. Determine the angular acceleration of the mass, assuming that it is constant.

## Homework Equations

honestly, this is my first problem. I figure that at least angular kinematics will come into play, but I'm not sure where to start...

I'm thinkin wf=0+a(lpha)t is where I'll want to go, since position is useless here.

## The Attempt at a Solution

well there's .397 rotations/second, for what it's worth.

.397 rot/s*2pi radians/rot=15.8rad/s.

so then I put that into the equation with the known value of time, but hey, that doesn't actually work. so I guess I did my rotation velocity incorrectly, but in all honesty, I don't know how to find that, because I don't really know how to approach this problem. it seems that the length of the string should come into play at some point, but I don't really know how.

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