Astronomy Practice Exam

What role does an external force play in the conservation of angular momentum?

1. An external force can increase angular momentum.

2. An external twisting force can change the angular momentum.

3. An external force has no effect on angular momentum.

4. An external force will always reduce angular momentum.

The correct answer is: An external twisting force can change the angular momentum.

An external twisting force, often referred to as a torque, plays a crucial role in altering the angular momentum of a system. Angular momentum is defined as the product of an object's rotational inertia and its angular velocity. When an external torque is applied, it can change this rotational state by either increasing or decreasing the angular momentum, depending on the direction and magnitude of the applied torque. In the absence of external torques, the total angular momentum of a system remains constant, adhering to the principle of conservation of angular momentum. However, when an external force applies a twisting action, it disrupts this balance, leading to a change in the system’s angular momentum. This principle is foundational in various applications in physics and engineering, highlighting how rotation can be influenced by external factors. The understanding of this concept is critical for studying rotational dynamics, where various factors like mass distribution, speed, and external forces all come into play, impacting how objects spin and move in space.