A soild wheel initially rotating at 50.0 rad/s comes to a uniform stop after 8.00 rotations.

Calculate the tangential accleration at the rim. Given that the angular acceleration is -24.9 rad/s^2.

I know its aT = r alpha but how do I get the radius?

The intial velocity was 50rad/sec* radius. The acceleration is -24.9*r m/s^2

vf^2=vi^2 + 2a*d

0=2500r^2+ 2(-24.9)r*2PIr*8
solve for r.

check my thinking.