Question

A figure skater on ice spins on one foot. She pulls in her arms and her rotational speed increases. Choose the best statement below.

1. Her angular speed increases because by pulling in her arms she creates a net torque in the direction of rotation.

2. Her angular speed increases because air friction is reduced as her arms come in.

3. Her angular speed increases because her angular momentum increases.

4. Her angular speed increases because her angular momentum is the same but her moment of inertia decreases.

5. Her angular speed increases due to a net torque exerted by her surroundings.

6. Her angular speed increases because her potential energy increases as her arms come in.​

Answer 1

Answer:4

Explanation:

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Answer 2

The rotational speed increases when the skater pulls her arms in because the moment of inertia decreases.

What is Angular momentum?

• It is the rotational momentum of the rotating object.

• It can be defined as the product of the moment of inertia and angular velocity.

$L = I \omega$

Where,

$L$ - Angular momentum

$I$ - moment of inertia = $mr^2$

$\omega$- angular velocity

From the equation, the angular velocity of the body is inversely proportional to the moment of inertia.

When the skater pulls her arms in, the moment of inertia decrease due to a decrease in radius,

Therefore, the rotational speed increases when the skater pulls her arms in because the moment of inertia decreases.

Learn more about Angular momentum:

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