Solve Sample Prob. 15.2, using the method of the instantaneous center of rotation.
a. Angular Velocity of the Gear. Since the gear rolls on the stationary lower rack, the point of contact C of the gear with the rack has no velocity; point C is therefore the instantaneous center of rotation. We write
v_A=r_A \text v \quad\quad\quad 1.2~ m / s =(0.150~ m ) \text vV = 8 rad/s i
b. Velocities. As far as velocities are concerned, all points of the gear seem to rotate about the instantaneous center.
Velocity of Upper Rack. Recalling that v_R=v_B, we write
v_R=v_B=r_B \text v \quad\quad\quad v_R=(0.250~ m )(8~ rad / s )=2~ m / s \\ \\ \text v _R=2~ m / s~\text yVelocity of Point D. Since r_D=(0.150~ m ) 1 \overline{2}=0.2121~ m , we write