Physics
posted by George on .
Rotating initially at 1800 rpm, a wheel with a diameter of 74.0 cm is brought to rest in 11.0 s. Calculate the magnitude of its angular acceleration in radians/second^2

The wheel radius makes no difference. They want an ANGULAR acceleration (or, in this case, deceleration) rate.
So, convert 1800 rpm to radians/s (which you surely know how to do) and divide the result by 11.0 seconds.
You should strictly put a minus sign in front of the number, to indicate deceleration. 
so do you not need the diameter for anything?

If you don't need the radius, you don't need the diameter