6.4 Conservation of Angular Momentum

Principle of Conservation of Angular Momentum

The conservation of angular momentum is a fundamental law of physics stating that if no external torque acts on a system, its total angular momentum remains constant. This principle is the rotational analogue of the conservation of linear momentum.

Angular momentum can only change when an external torque exerts an angular impulse on the system. Internal torques, such as forces between parts of the system, always cancel out and do not affect the system’s total angular momentum.

Important Equation: ${L_{tot, , initial} = L_{tot, , final}}$

or equivalently, ${\Delta L_{tot} = 0 , \text{ (if } \tau_{ext} = 0)}$