Conservation of Angular Momentum (Inertia Definition)
Reference from the original Physics I textbook.
- Conservation of Angular Momentum (Inertia Definition)
For rotation about one fixed axis with zero net external torque about that axis: I_iω_i = I_fω_f.
- Related Glossary Terms
Angular Momentum↗, Angular Momentum of a Rigid Body Equation, Conservation of Angular Momentum
- Index
Reviewed physics notes (1)
These corrections keep the original lesson’s purpose while fixing errors in the source edition.
- Conservation requires zero net external torque and a consistent axis. — Reference 1
Glossary and deeper reading · 3 refreshers
These editorial refreshers supplement the reading. Definitions and examples are added guidance; original source wording and recorded answers remain in their original context.
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Conservation of angular momentum
Angular momentum is conserved about a chosen axis when the net external angular impulse about that axis is zero. Internal interactions can change the distribution of mass and the rotation rates of parts without changing the total. For example, a rotating skater who pulls their arms inward can spin faster as their rotational inertia decreases.
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Inertia
Inertia is an object’s resistance to a change in its velocity. Mass measures translational inertia, whereas rotational inertia also depends on how mass is distributed relative to an axis. For example, a loaded cart accelerates less than an empty cart under the same net force.
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Angular momentum
Angular momentum describes motion about a specified point or axis. For rigid rotation about a fixed principal axis it can be written as rotational inertia times angular velocity; a translating particle can also have angular momentum about a point. For example, a ball moving past a pole has angular momentum about the pole even though the ball’s path is straight.