Characteristic of rotational motion. 

In rotation of a rigid body about a fixed axis, every particle of the body moves in a circle which lies in a plane perpendicular to the axis and has its centre on the axis.

In figure, rotational motion of a rigid body shows about the $Z$-axis of the frame of reference. Let $\mathrm{P}_{1}$ be a particle of the rigid body, arbitrarily chosen and at a distance $r_{1}$ from the fixed axis. The particle $\mathrm{P}_{1}$ describe a circle of radius $r_{1}$ with its centre $\mathrm{C}_{1}$ on the fixed axis. The circle lies in a plane perpendicular to the axis.

An another particle $\mathrm{P}_{2}$ of the rigid body, $\mathrm{P}_{2}$ is at a distance $r_{2}$ from the fixed axis. The particle $\mathrm{P}_{2}$ moves in a circle of radius $r_{2}$ and with centre $\mathrm{C}_{2}$ on the axis.

The circles described by $P_{1}$ and $P_{2}$ may lie in different planes, both these planes are perpendicular to the fixed axis.

For any particle on the axis like $\mathrm{P}_{3}, r_{3}=0$. Any such particle remains stationary while the body rotates.

In rotation of a spinning top, the axis may not be fixed as shown in figure. Assume that spinning top rotates at a fixed place.