- If a rigid body rotates around a fixed axis, its angular momentum is oriented along the rotation axis
- It often helps to arrange the coordinate axes so that a body rotates in the xy-plane, so that angular momentum is entirely along the z-axis.
- When a rigid body rotates around a fixed axis, its angular
momentum around that axis can be expressed as
angular momentum = (moment of inertia) * (angular velocity)

- When a rigid body rotates around a fixed axis, the derivative
with respect to time of its angular momentum around
that axis can be expressed as
dL/dt = (moment of inertia) * (angular accleration) = sum of external torques

- If the sum of external torques on a body around some axis is zero, then its angular momentum around that axis is constant.
- If such a body changes its moment of inertia, its angular velocity must change to keep angular momentum constant.

This lecture discusses material in Chapter 11 of Serway.

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Copyright © Michael Richmond. This work is licensed under a Creative Commons License.