Chapter 12, Problem 8A

How does a skater decrease his or her rotational inertia while spinning?

To determine

The way in which a skater decrease his or her rotational inertia while spinning.

Answer to Problem 8A

By increasing its rotational speed.

Explanation of Solution

Introduction:

When no external torque acts on a system, then the angular momentum of the system remains conserved.

The angular momentum is given by,

  $L=I\omega$

Where,

  $I=$ rotational inertia

  $\omega$ = rotational speed

Since no external torque is exerted on the skater, hence his or her angular momentum remains conserved.

Now, if the rotational speed of the skater is increased while spinning, then considering the above mentioned formula, the rotational inertia will decrease.

Conclusion:

Hence, to decrease the rotational inertia, the rotational speed of the skater must be increased while spinning.