Two friction disks are shown in Fig. 2-22. Derive the expression for the angular velocity ratio in terms of the radii.
The linear velocities of the mating points A and B on the two wheels are equal. If this were not true, the wheels would slip relative to each other. The linear velocities of points A and B are, respectively,
v_{A}=R_{1} \omega_{1} \qquad v_{B}=R_{2} \omega_{2}
But v_{A}=v_{B} if the drive is positive, i.e., without slip. Then
R_{1} \omega_{1}=R_{2} \omega_{2} \quad \text { or } \quad \frac{\omega_{1}}{\omega_{2}}=\frac{R_{2}}{R_{1}}