91Ó°ÊÓ

Horizontal disk rotating counter-clockwise with a beetle on it.

Use the concept of angular momentum and angular velocity. There is a proportional relation between the angular velocity and linear velocity.

The formula is as follows:

$L=I\mathrm{Ó\neg }$

WhereL is angular momentum, I is a moment of inertia and $\mathrm{Ó\neg }$is angular velocity.

When a beetlewalks along with a disk in the direction of rotation, it will have a little more angular velocity but it will decrease the angular velocity of the disk, so finally, the angular momentum of the beetle and disk remains the same.

In this case, if seen separately, beetles will have more angular velocity and hence the angular momentum. But for a disk, the angular velocity decreases little and so does the angular momentum.

If the beetle walks opposite the direction of rotation the angular momentum and velocity of the beetle will decrease while the angular momentum and angular velocity of the disk will increase.

Whether the angular momentum and angular velocity increase, decrease, or remain the same can be found depending on the direction of the motion of the object.

When the beetle walks in the opposite direction of the rotation, the angular momentum of the beetle-disk system will remain the same, its angular momentum and angular velocity of the beetle will decrease while that of the disk will increase.