Conservation of Angular Momentum

Definition

Conservation of angular momentum is a fundamental principle in physics that states the total angular momentum of a closed system remains constant unless an external torque is applied. This principle is essential in understanding the behavior of rotational motion and the dynamics of spinning objects.

5 Must Know Facts For Your Next Test

1. The conservation of angular momentum states that the total angular momentum of a closed system remains constant unless an external torque is applied.
2. In the absence of external torques, the angular momentum of a rotating object is conserved, meaning it will continue to rotate at the same angular velocity.
3. The conservation of angular momentum is a key principle in understanding the behavior of rotating systems, such as planets, stars, and atoms.
4. When an external torque is applied to a rotating object, the angular momentum of the system changes, and this change is proportional to the applied torque and the time over which it acts.
5. The conservation of angular momentum is a fundamental concept in the study of rotational dynamics, including topics like torque, work, and power for rotational motion, as well as the precession of gyroscopes.

Review Questions

• Explain how the conservation of angular momentum is related to the concept of torque.
  • The conservation of angular momentum is closely tied to the concept of torque. Torque is the rotational force that causes an object to rotate, and it is this torque that can change the angular momentum of a system. When no external torque is applied to a closed system, the total angular momentum of that system remains constant. However, if an external torque is applied, it will cause a change in the angular momentum of the system, with the change in angular momentum being proportional to the applied torque and the time over which it acts.
• Describe how the conservation of angular momentum is related to the concepts of work and power for rotational motion.
  • The conservation of angular momentum is an important principle in understanding the work and power associated with rotational motion. When a torque is applied to a rotating object, it does work on the object, changing its angular momentum. This work is equal to the change in the object's angular momentum multiplied by the perpendicular distance from the axis of rotation to the line of action of the force. The power required to maintain this rotational motion is the rate at which this work is done, which is the product of the torque and the angular velocity of the object. The conservation of angular momentum ensures that the total angular momentum of the system is preserved, even as work is done and power is expended to maintain the rotation.
• Analyze how the conservation of angular momentum is a key principle in understanding the precession of a gyroscope.
  • The precession of a gyroscope is a prime example of the application of the conservation of angular momentum. When a gyroscope is spinning, it has a certain amount of angular momentum. If an external torque is applied to the gyroscope, such as the force of gravity, the gyroscope will not simply change its axis of rotation. Instead, the gyroscope will precess, or rotate, around an axis perpendicular to both the applied torque and the original axis of rotation. This precession occurs because the gyroscope is trying to conserve its angular momentum in the face of the external torque. The rate of precession is inversely proportional to the gyroscope's angular momentum, demonstrating the fundamental role that the conservation of angular momentum plays in the behavior of spinning objects like gyroscopes.

Related terms

Angular Momentum:

Angular momentum is a measure of the rotational motion of an object, calculated as the product of the object's moment of inertia and its angular velocity.

Torque:

Torque is the rotational force that causes an object to rotate about an axis, fulcrum, or pivot. It is the product of the force and the perpendicular distance from the line of action of the force to the axis of rotation.

Precession:

Precession is the phenomenon where the axis of a spinning object, such as a gyroscope, slowly rotates around another axis due to the application of an external torque.