AP Physics 1 Flashcards: Conservation Of Angular Momentum

What this deck covers

This deck focuses on Conservation Of Angular Momentum, giving you a quick way to review the definitions, rules, and examples that matter most for AP Physics 1.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What happens to a wheel's angular momentum if its speed triples?

Answer: Angular momentum triples. Angular momentum is directly proportional to angular velocity.

Flashcard 2: What does $\omega$ represent in the formula $L = I\omega$?

Answer: Angular velocity. Rate of rotation measured in radians per second.

Flashcard 3: State the effect of an increase in rotational speed on moment of inertia.

Answer: No effect; moment of inertia is mass and shape dependent. Moment of inertia depends only on mass distribution.

Flashcard 4: State the conservation of angular momentum principle.

Answer: Total angular momentum remains constant if no external torque acts. Fundamental principle when no external torques act on system.

Flashcard 5: Define the term 'torque'.

Answer: A measure of the force that can cause an object to rotate about an axis. Rotational analog of force for linear motion.

Flashcard 6: Calculate the angular momentum of a 2 kg mass moving at 4 m/s in a circle of radius 0.5 m.

Answer: $L = 4 \text{ kg} \cdot \text{m}^2/\text{s}$. $L = mvr = 2 \times 4 \times 0.5 = 4$ units.

Flashcard 7: Identify the formula for angular momentum of a rotating body.

Answer: $L = I\omega$. For rigid bodies: moment of inertia times angular velocity.

Flashcard 8: What happens to angular momentum when net external torque is applied?

Answer: Angular momentum changes. External torque causes rate of change in angular momentum.

Flashcard 9: What is the formula for angular momentum $L$ of a point mass?

Answer: $L = mvr \sin \theta$. For point mass: momentum times radius times sine of angle.

Flashcard 10: How does angular velocity change if the radius is halved while conserving angular momentum?

Answer: Angular velocity quadruples. Since $I = mr^2$, halving $r$ quarters $I$, so $\omega$ quadruples.

Flashcard 11: If a spinning disk's moment of inertia increases, what happens to its angular velocity?

Answer: Angular velocity decreases. Since $L = I\omega$, larger $I$ requires smaller $\omega$.

Flashcard 12: What is the unit of angular momentum in the SI system?

Answer: Kilogram meter squared per second ($\text{kg} \cdot \text{m}^2/\text{s}$). Derived from $L = mvr$ with standard SI base units.

Flashcard 13: What condition must be met for angular momentum to be conserved?

Answer: No net external torque. Zero net torque is required for conservation.

Flashcard 14: What is the effect of decreasing radius on angular velocity if $L$ is constant?

Answer: Angular velocity increases. Since $L = I\omega = mr^2\omega$, smaller $r$ requires larger $\omega$.

Flashcard 15: What is the effect of friction on angular momentum?

Answer: Friction can reduce angular momentum by exerting external torque. Creates external torque that opposes rotational motion.

Flashcard 16: What is the relationship between torque and change in angular momentum?

Answer: $\tau = \frac{dL}{dt}$. Torque equals the time rate of change of angular momentum.

Flashcard 17: What is the effect of a net external force on a system's angular momentum?

Answer: It can change the system's angular momentum. External forces can create torques that change $L$.

Flashcard 18: Identify the variable that represents angular velocity.

Answer: $\omega$. Greek omega represents angular velocity in physics.

Flashcard 19: Define moment of inertia for a point mass.

Answer: $I = mr^2$. Mass times distance squared from rotation axis.

Flashcard 20: For a rotating rod, what is the expression for its moment of inertia about its end?

Answer: $I = \frac{1}{3}mL^2$. Standard formula for rod rotating about one end.

Flashcard 21: What does $I$ represent in the angular momentum formula $L = I\omega$?

Answer: Moment of inertia. Rotational inertia - resistance to angular acceleration.

Flashcard 22: What happens to a figure skater's angular momentum when they pull their arms in?

Answer: Remains constant. Conservation applies - only $I$ and $\omega$ change, not $L$.

Flashcard 23: What is the relationship between angular momentum and linear momentum?

Answer: Angular momentum is the rotational analog of linear momentum. Both describe inertial motion in their respective domains.

Flashcard 24: What does $\omega$ represent in the formula $L = I\omega$?

Answer: Angular velocity. Rate of rotation measured in radians per second.

Flashcard 25: How does angular momentum conservation apply to a collapsing star?

Answer: Angular velocity increases as the star's radius decreases. Conservation requires $\omega$ to increase as radius shrinks.

Flashcard 26: What occurs when a rotating object experiences a change in distribution of mass?

Answer: Its moment of inertia changes. Redistributing mass changes the moment of inertia $I$.

Flashcard 27: What is the effect of increasing moment of inertia on a system's stability?

Answer: Stability increases. Larger $I$ resists changes in rotational motion.

Flashcard 28: How does doubling the mass of a rotating object affect its angular momentum?

Answer: Angular momentum doubles. Since $L = I\omega$ and $I = mr^2$, doubling $m$ doubles $L$.

Flashcard 29: Calculate angular momentum change if torque is applied for time $t$.

Answer: $\Delta L = \tau t$. Impulse-momentum theorem applied to rotational motion.

Flashcard 30: What is the formula for torque $\tau$?

Answer: $\tau = rF \sin \theta$. Force times lever arm times sine of angle between them.