State and explain the law of conservation of angular momentum. Give two examples to illustrate the law.
Law of conservation of angular momentum states that
The total angular momentum of an isolated system remains constant both in magnitude & direction.
Where I is moment of inertia for angular velocity ω &I is moment of inertia for angular velocity ω
1
1
2
2
i.e., I ω = I ω
1
1
2
2
Illustration 1
A spinning ballet dancer - Dancers first spin their arms and one of the legs where the moment of inertia about the axis of rotation is large & thus angular velocity is small.
Continues
Then they fold their arms and bring down the stretched leg to the other leg. This results in a decrease in the moment of inertia and an increase in the angular speed.
Illustration 2
A diver jumping from a springboard - He folds his arms & legs inwards & curls his body. So the moment of inertia decreases. He then somersaults in the air with a high angular speed.
Continues
While touching the surface of the water, he stretches his limbs resulting in an increase in his moment of inertia & a decrease in his angular speed. So, he touches the water at a lower speed.