State the principle of conservation of angular momentum .

The total angular momentum of an isolated system remains constant unless acted on by a net external torque .

Conservation of angular momentum is a direct result of .......... .

Conservation of angular momentum is a direct result of Newton's third law .

True or False? The total angular momentum of a system is conserved even when a nonzero net external torque acts on it.

False. A net external torque transfers angular momentum between the system and its surroundings, so conservation of angular momentum is not valid for that system.

What happens to the angular speed of a nonrigid system when it moves mass closer to its rotational axis?

Its rotational inertia decreases , so its angular speed increases (assuming no external torque).

The total angular momentum of a system is the .......... of the angular momenta of its constituent parts.

The total angular momentum of a system is the sum of the angular momenta of its constituent parts.

Define isolated system .

An isolated system is a system on which the net external torque is zero , so its total angular momentum is constant.

What is the only way to change the total angular momentum of a system?

Apply a net external torque . Any change is then due to a transfer of angular momentum between the system and its surroundings.

True or False? When an ice skater pulls in their arms, their angular momentum increases.

False. With no external torque, angular momentum stays constant . Pulling in the arms decreases the rotational inertia , so the angular speed increases instead.

AP®PhysicsCollege BoardPhysics 1: Algebra-BasedFlashcardsUnit 6: Energy & Momentum of Rotating SystemsConservation of Angular Momentum

Conservation of Angular Momentum (College Board AP® Physics 1: Algebra-Based): Flashcards

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FrontConservation of Angular Momentum
State the principle of conservation of angular momentum.
FrontConservation of Angular Momentum
What equation expresses conservation of angular momentum for an interaction between objects in an isolated system?
BackConservation of Angular Momentum
$\sum L_{i} = \sum L_{f}$
$L_{i}$ = initial angular momentum, before the interaction (kg·m²/s)
$L_{f}$ = final angular momentum, after the interaction (kg·m²/s)

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Cards in this collection (15)

State the principle of conservation of angular momentum.
The total angular momentum of an isolated system remains constant unless acted on by a net external torque.
What equation expresses conservation of angular momentum for an interaction between objects in an isolated system?
$\sum L_{i} = \sum L_{f}$
- $L_{i}$ = initial angular momentum, before the interaction (kg·m²/s)
- $L_{f}$ = final angular momentum, after the interaction (kg·m²/s)
A dart of mass m strikes a tire at radius R with velocity v at angle θ to the radius. What is the dart's angular momentum about the axis?
$L = m v R sin θ$
State the equation for angular impulse.
$angular impulse = ∆ L$
- $∆ L$ = change in angular momentum of the system (kg·m²/s)
- angular impulse is measured in N·m·s
When two objects interact, how do their changes in angular momentum compare, and why?
$∆ L_{A} = - ∆ L_{B}$
The torques the objects exert on each other are equal in magnitude and opposite in direction and act for the same time interval.
Conservation of angular momentum is a direct result of ...........
Conservation of angular momentum is a direct result of Newton's third law.
True or False?
The total angular momentum of a system is conserved even when a nonzero net external torque acts on it.
False.
A net external torque transfers angular momentum between the system and its surroundings, so conservation of angular momentum is not valid for that system.
Why can a nonrigid system change its angular speed when it changes shape?
Changing shape changes the distribution of mass about the rotational axis, so its rotational inertia changes. To conserve angular momentum ( $L = I ω$ ), its angular speed must change too.
What happens to the angular speed of a nonrigid system when it moves mass closer to its rotational axis?
Its rotational inertia decreases, so its angular speed increases (assuming no external torque).
State the equation for conservation of angular momentum in a nonrigid system.
$I_{i} ω_{i} = I_{f} ω_{f}$
- $I_{i}$ = initial rotational inertia (kg·m²)
- $ω_{i}$ = initial angular velocity (rad/s)
- $I_{f}$ = final rotational inertia (kg·m²)
- $ω_{f}$ = final angular velocity (rad/s)
State the equation for the total rotational inertia of a system of particles.
$I = \sum_{i} m_{i} r_{i}^{2}$
- $m_{i}$ = mass of particle i (kg)
- $r_{i}$ = distance of particle i from the rotational axis (m)
The total angular momentum of a system is the .......... of the angular momenta of its constituent parts.
The total angular momentum of a system is the sum of the angular momenta of its constituent parts.
Define isolated system.
An isolated system is a system on which the net external torque is zero, so its total angular momentum is constant.
What is the only way to change the total angular momentum of a system?
Apply a net external torque. Any change is then due to a transfer of angular momentum between the system and its surroundings.
True or False?
When an ice skater pulls in their arms, their angular momentum increases.
False.
With no external torque, angular momentum stays constant. Pulling in the arms decreases the rotational inertia, so the angular speed increases instead.

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