Question

A swimmer while jumping into water from height easily forms a loop in the air so as to _____
1. decrease moment of inertia & increase angular speed
2. decrease moment of inertia & decrease angular speed
3. increase moment of inertia & increase angular speed
4. increase moment of inertia & decrease angular speed​

Answer 1

Answer:

The Correct answer is 1. decrease moment of inertia & increase angular speed

Explanation:

by pulling his arms and legs in he decreases his moment of inertia, thereby increasing his angular velocity using the principle of conservation of angular momentum.

Answer 2

1. Decrease moment of inertia & increase angular speed.

But why ?

• When a swimmer is diving , he/she does not experience any external torque. As a result, his angular momentum remains constant.

• Angular momentum is a product of momentum of inertia and angular velocity.

$\boxed{L = I \times \omega = constant}$

• Hence, the swimmers brings his/her hands and feet closer to his body. This reduces the moment of Inertia.

• When moment of inertia reduces, the angular velocity increases and the diver is able to make many turns.

Hope It Helps