Conservation of Angular Momentum Quiz with Answers: Test Your Knowledge

📚 Quick Study Guide

• 🎡 Definition: Angular momentum ($L$) is a vector quantity representing the rotational momentum of a body.
• 📐 Formula: $L = I \omega$, where $I$ is the moment of inertia and $\omega$ is the angular velocity.
• 🧮 Conservation Law: In a closed system, the total angular momentum remains constant if no external torque acts on it. Mathematically, $L_{initial} = L_{final}$.
• 💡 Moment of Inertia: A measure of an object's resistance to rotational acceleration. For a point mass, $I = mr^2$.
• 🔄 Angular Velocity: The rate of change of angular displacement, measured in radians per second (rad/s).
• 🔑 Key Applications: Spinning ice skaters, rotating planets, and many other physical systems.

Practice Quiz

1. A spinning ice skater pulls their arms inward. What happens to their angular speed?
   1. It decreases.
   2. It increases.
   3. It remains constant.
   4. It becomes zero.
2. Which of the following is an example of conservation of angular momentum?
   1. A car accelerating on a straight road.
   2. A ball thrown vertically upwards.
   3. A satellite orbiting the Earth.
   4. A book resting on a table.
3. A rotating object has its moment of inertia doubled. To conserve angular momentum, what must happen to its angular velocity?
   1. It must double.
   2. It must halve.
   3. It must remain the same.
   4. It must quadruple.
4. What condition must be met for angular momentum to be conserved?
   1. The system must be isolated.
   2. No external force acts on the system.
   3. The system must be at rest.
   4. The temperature must be constant.
5. A point mass $m$ rotates with velocity $v$ at radius $r$. What is its angular momentum?
   1. $mr$
   2. $mv$
   3. $mvr$
   4. $\frac{mv}{r}$
6. If a spinning top experiences friction, does its angular momentum remain constant?
   1. Yes, always.
   2. No, because friction exerts a torque.
   3. Yes, if the friction is minimal.
   4. It depends on the top's mass.
7. Two identical disks are rotating at the same angular speed. One is made of steel, and the other is made of plastic. Which has a larger angular momentum?
   1. The steel disk.
   2. The plastic disk.
   3. They have the same angular momentum.
   4. It depends on their radii.