College Physics II – Mechanics, Sound, Oscillations, and Waves
Definition
The law of conservation of angular momentum states that if no external torque acts on a system, the total angular momentum of the system remains constant. This principle is crucial in understanding rotational dynamics.
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Angular momentum is given by the product of the moment of inertia and angular velocity: $L = I \omega$.
In an isolated system with no external torques, the initial angular momentum equals the final angular momentum: $L_{initial} = L_{final}$.
This law can be observed in various phenomena such as a spinning figure skater pulling in their arms to spin faster.
External torques can change the angular momentum of a system; internal forces cannot.
Conservation of angular momentum explains why planets continue to orbit stars without needing an external force.
Review Questions
What is the mathematical expression for angular momentum?
How does an external torque affect a system's angular momentum?
Give an example where conservation of angular momentum is clearly observed.
Related terms
Torque: A measure of how much a force acting on an object causes that object to rotate. It is given by $\tau = r \times F$.
Moment of Inertia: A measure of an object's resistance to changes in its rotation rate, dependent on mass distribution relative to the axis of rotation.
Angular Velocity: The rate at which an object rotates or revolves around another point, expressed in radians per second ($\omega$).
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