Question

State the law of conservation of angular momentum and explain with a suitable example.

Answer 1

Angular momentum (L):

1. It can be stated as the product of the linear momentum of a body and its distance from its rotation point, $L=pr$.

Law of conservation of angular momentum:

1. It states that “For a spinning system, there is no change in the angular momentum of the object until and unless an external torque is applied to it.”
2. Therefore, it can be stated that the velocity of the rotation will remain constant as long as the net torque applied is equal to zero.

Example of conservation of angular momentum:

1. The spinning of Earth on its axis at the same rate for billions of years-Here, the speed of the earth is more near the sun and comparatively less when it is away from the sun, in an elliptical orbit. Due to this, angular momentum is conserved ($L=mvr$). Here,$m$is the mass of the earth,$v$ its velocity, and $r$ is the distance from the sun
2. The spinning of an ice skater.-In this case, an ice-skater changes her velocity by holding her arms outwards or pulling them inwards. When she pulls her hands in, her inertia decreases. Since there is no external force acting on her, angular momentum is conserved as her velocity magnitude increases.