AP Physics C: Mechanics Flashcards: Conservation of Angular Momentum
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
What is the fundamental condition required for the total angular momentum of a system to be constant?
The total angular momentum of a system is constant if the net external torque exerted on that selected object or rigid system is zero.
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What is the fundamental condition required for the total angular momentum of a system to be constant?
The total angular momentum of a system is constant if the net external torque exerted on that selected object or rigid system is zero.
What is the exclusive cause for a change in a system's angular momentum?
Any change to a system’s angular momentum must be due to an interaction between the system and its surroundings that produces a net external torque.
How does the choice of a 'system' impact the analysis of its angular momentum?
The selection of a system is critical because it determines which forces and torques are internal versus external; only net external torques can change the system's angular momentum.
How can the principle of conservation of angular momentum be used to describe a system's behavior?
If a system has zero net external torque, we can describe its behavior by stating that its total angular momentum remains constant, even if its shape or speed of rotation changes.
A student is on a frictionless rotating stool. If they are the system, what must be true for their angular momentum to change?
For the student's angular momentum to change, there must be an interaction with the surroundings (like pushing off a wall) that creates a net external torque on them.
Can torques exist *within* a system without changing its total angular momentum?
Yes, internal torques can exist, but as long as the net *external* torque is zero, the total angular momentum of the system remains constant.
State the principle of conservation of angular momentum.
If the net external torque exerted on a selected system is zero, then the total angular momentum of that system is constant.
A spinning satellite in deep space retracts its solar panels. If the satellite is considered the system, why is its angular momentum conserved?
Assuming no external forces from other celestial bodies create a net torque, the satellite's angular momentum is conserved because there is no net external torque acting on the system.
What is meant by 'constant angular momentum'?
Constant angular momentum means the total angular momentum of a system does not change over time, which occurs when the net external torque on the system is zero.
Explain the relationship between an external interaction and angular momentum.
An interaction between a system and its surroundings can create a net external torque, which is the mechanism that causes the system's total angular momentum to change.