Pottery wheel, angular acceleration, and required speed

[SereneKi]

Homework Statement

a small rubber wheel is used to drive a large pottery wheel, and they are mounted so that they touch. if the small wheel has a radius of 2.01 cm and accelerates at a rate of 7.08 rad/s^2 and is in contact with the pottery wheel (24.2 cm) without slipping, find the angular acceleration of the pottery wheel and find the time it takes it to reach 67.4 rpm?

Homework Equations

w=w0+at

The Attempt at a Solution

I've already found the acceleration of the pottery wheel to be 0.588 rad/s^2 but I'm having trouble with the 2nd part

r1=0.0201 m
r2=0.242 m
alpha1=7.08 rad/s^2
alpha2=0.588 rad/s^2

w2 = 67.4 rpm -> 3.53 rad/s

w=w0+at
3.53=0+(0.588)t
t=6.003 s

what am I doing wrong?

 

[tiny-tim]

Hi SereneKi!

w2 = 67.4 rpm -> 3.53 rad/s

nooo … one revolution = two π