# What is Radius of Gyration in Physics | Definition, Formula – Rotational Motion

Radius of Gyration Meaning:
The root mean square distance of its constituent particles from the axis of rotation is called the radius of gyration of a body. It is denoted by K.

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## What is Radius of Gyration in Physics | Definition, Formula – Rotational Motion

Radius of gyration Formula:

K = $$\sqrt{\frac{r_{1}^{2}+r_{2}^{2}+\ldots+r_{n}^{2}}{n}}$$

The Radius of Gyration of a Body about an Axis:
The product of the mass of the body (M) and square of its radius of gyration (K) gives the same moment of inertia of the body about the rotational axis.

Radius of Gyration Moment of Inertia:
Therefore, moment of inertia, I = MK² ⇒ K = $$\sqrt{\frac{I}{M}}$$

Rotational Motion:
In this portion, we will learn about the rotational motion of the objects. A body moves completely in rotational motion when each particle of the body moves in a circle about a single line. When a force is applied on a body about an axis it causes a rotational motion. The force applied here is called the torque. The axis of the rotation usually goes through the body. Also, learn the two theorems such as parallel axes and perpendicular theorem explained with respect to rotational motion of objects.