Rotational Motion

Home Center of mass Rotations Angular Acceleration Kinematics Torque Rotational Mass

Assume that you are replacing the bearings in the wheel of your bicycle.  To test if you have done a good job, you hold the axle vertically and give it a spin.  The axle at the center of the wheel is stationary.  The wheel as a whole has no translational motion.  But the wheel is turning around the axle.  Every point on the wheel undergoes circular motion about an axis of rotation.  Such motion around an axis of rotation is called rotational motion.

Extended object can have translational and rotational motion.  Any motion of an extended object can be viewed as a combination of translational motion of the center of mass and rotational motion about the center of mass.

Example:

A foam square has a blue LED near its CM and a red LED near its edge.  If we toss the sponge we can easily observe the parabolic motion of the CM and the rotational motion about the CM.

Sponge Toss Movie