# 13 Lecture

## PHY101

### Midterm & Final Term Short Notes

## Angular Momentum

Angular momentum is a fundamental concept in physics that arises in the context of rotating systems. It is a vector quantity that describes the rotational motion of an object, and it plays a key role in a variety of physical phenomena, from the

**Important Mcq's**

Midterm & Finalterm Prepration

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**Which of the following statements is true about angular momentum?**

A. It is a scalar quantity.

B. It is a vector quantity.

C. It is a measure of an object's rotational inertia.

D. It is the product of an object's mass and velocity.

Answer: B. It is a vector quantity.

**Which of the following is an example of conservation of angular momentum?**

A. A spinning top eventually comes to a stop.

B. A figure skater spins faster when she pulls her arms in.

C. A car's wheels stop rotating when the brakes are applied.

D. A basketball player's shot is affected by the spin he puts on the ball.

Answer: B. A figure skater spins faster when she pulls her arms in.

**Which of the following statements is true about the direction of angular momentum?**

A. It is always perpendicular to the plane of rotation.

B. It is always in the same direction as the angular velocity.

C. It can be in any direction relative to the plane of rotation.

D. It depends on the direction of the applied torque.

Answer: C. It can be in any direction relative to the plane of rotation.

**Which of the following is a unit of angular momentum?**

A. meters per second

B. newtons

C. joules

D. kilograms meters squared per second

Answer: D. kilograms meters squared per second

**Which of the following is an example of a system with no net angular momentum?**

A. A spinning top

B. The Earth revolving around the Sun

C. A bicycle wheel in motion

D. A figure skater spinning on one leg

Answer: B. The Earth revolves around the Sun

**Which of the following is an example of an object with zero angular momentum?**

A. A planet orbiting the Sun

B. A ball rolling down a hill

C. A spinning top

D. A car driving on a straight road

Answer: D. A car driving on a straight road

**Which of the following statements is true about the conservation of angular momentum?**

A. It is only conserved in isolated systems.

B. It is always conserved in any system.

C. It is only conserved in systems with no external torques.

D. It is not a conserved quantity.

Answer: B. It is always conserved in any system.

**Which of the following is an example of a system with changing angular momentum?**

A. A satellite in circular orbit around the Earth

B. A pendulum swinging back and forth

C. A ball bouncing off a wall

D. A figure skater spinning at a constant rate

Answer: C. A ball bouncing off a wall

**Which of the following statements is true about the moment of inertia?**

A. It is a measure of an object's mass.

B. It is a measure of an object's resistance to rotational motion.

C. It is the same for all objects.

D. It is always equal to the object's radius.

Answer: B. It is a measure of an object's resistance to rotational motion.

**Which of the following is an example of an object with high moment of inertia?**

A. A thin hoop

B. A thin rod

C. A solid sphere

D. A hollow sphere

Answer: D. A hollow sphere

**Subjective Short Notes**

Midterm & Finalterm Prepration

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**What is angular momentum?**

Angular momentum is a measure of an object's rotational motion. It is a vector quantity that depends on both the object's moment of inertia and its angular velocity.

**How is angular momentum related to torque?**

Angular momentum is directly proportional to torque, which is the force that causes an object to rotate. The greater the torque applied to an object, the greater its angular momentum will be.

**How is angular momentum conserved?**

Angular momentum is conserved when there is no external torque acting on a system. This means that the total angular momentum of a system before an event will be equal to the total angular momentum after the event.

**What is the difference between linear momentum and angular momentum?**

Linear momentum is a measure of an object's motion in a straight line, while angular momentum is a measure of an object's rotational motion. Linear momentum depends on an object's mass and velocity, while angular momentum depends on its moment of inertia and angular velocity.

**What is a moment of inertia?**

Moment of inertia is a measure of an object's resistance to rotational motion. It depends on the object's mass distribution and its shape. Objects with a larger moment of inertia require more torque to produce the same angular acceleration as objects with a smaller moment of inertia.

**How does the moment of inertia affect an object's angular momentum?**

The moment of inertia affects an object's angular momentum by determining how quickly it can rotate for a given amount of torque. Objects with a larger moment of inertia will have a smaller angular velocity for a given torque and thus a smaller angular momentum.

**What is the conservation of angular momentum?**

The conservation of angular momentum states that the total angular momentum of a system is conserved when there is no external torque acting on the system. This means that the sum of the angular momenta of all the objects in the system will remain constant.

**How is angular momentum related to the Earth's rotation?**

The angular momentum of the Earth's rotation is what keeps it spinning on its axis. The Earth's moment of inertia and its rotation rate determine its angular momentum.

**How do you calculate angular momentum?**

Angular momentum is calculated by multiplying an object's moment of inertia by its angular velocity. The equation for angular momentum is L = I?, where L is the angular momentum, I is the moment of inertia, and ? is the angular velocity.

**How can you increase an object's angular momentum?**

An object's angular momentum can be increased by either increasing its angular velocity or increasing its moment of inertia. This can be achieved by applying torque to the object or by changing its shape or mass distribution.

### Angular momentum

Angular momentum is a fundamental concept in physics that arises in the context of rotating systems. It is a vector quantity that describes the rotational motion of an object, and it plays a key role in a variety of physical phenomena, from the motion of celestial bodies to the behavior of subatomic particles. Angular momentum is defined as the product of the moment of inertia of an object and its angular velocity. The moment of inertia describes an object's resistance to rotational motion, while angular velocity is the rate at which an object rotates about an axis. The angular momentum vector points in the direction of the axis of rotation and has a magnitude equal to the product of the moment of inertia and the angular velocity. In classical mechanics, angular momentum is conserved in the absence of external torques. This means that the total angular momentum of a system of particles remains constant, even as the individual particles undergo rotational motion. This conservation law has many important consequences, including the ability to predict the behavior of rotating systems, such as gyroscopes and spinning tops. One important application of angular momentum is in the study of celestial mechanics. The angular momentum of planets and other celestial bodies plays a key role in their orbits around the sun. Because the total angular momentum of a system is conserved, any changes in the distribution of angular momentum within the system can result in changes in the orbits of the individual bodies. Another important application of angular momentum is in the study of subatomic particles. In quantum mechanics, angular momentum is quantized, meaning that it can only take on certain discrete values. This leads to the concept of spin, which is a type of intrinsic angular momentum possessed by subatomic particles. Spin plays a key role in determining the behavior of particles in particle accelerators and other high-energy physics experiments. Angular momentum also plays a role in the behavior of macroscopic objects, such as cars and bicycles. For example, when a car turns a corner, the wheels must rotate at different speeds in order to maintain a constant angular momentum about the center of mass of the car. Similarly, a bicycle rider can change the direction of the bike by applying torque to the handlebars, which changes the angular momentum of the bike and causes it to turn.**In summary,**angular momentum is a fundamental concept in physics that arises in the context of rotating systems. It is a vector quantity that describes the rotational motion of an object and plays a key role in a wide variety of physical phenomena, from the behavior of celestial bodies to the behavior of subatomic particles. Understanding the principles of angular momentum is essential for predicting the behavior of rotating systems and for understanding the behavior of the physical world around us.