# inertia

> The Rigidbody's resistance to changes in angular velocity (rotation).

## Definition

* **Type:** Property
* **Namespace:** [UnityEngine](/engine/6000.0/script-reference/unityengine.md)
* **Assembly:** UnityEngine.Physics2DModule

```csharp
public float inertia { get; set; }
```

### Remarks

Rotational inertia controls a Rigidbody's resistance to changes in [Rigidbody2D.angularVelocity](/engine/6000.0/script-reference/unityengine/rigidbody2d/angularvelocity.md). It is similar to how [Rigidbody2D.mass](/engine/6000.0/script-reference/unityengine/rigidbody2d/mass.md) controls a Rigidbody's resistance to changes in [Rigidbody2D.linearVelocity](/engine/6000.0/script-reference/unityengine/rigidbody2d/linearvelocity.md).

The rotational inertia is automatically calculated based on the Rigidbody's [Rigidbody2D.mass](/engine/6000.0/script-reference/unityengine/rigidbody2d/mass.md) position relative to the [Rigidbody2D.centerOfMass](/engine/6000.0/script-reference/unityengine/rigidbody2d/centerofmass.md).  It can also be specified explicitly by setting this property in the same way [Rigidbody2D.mass](/engine/6000.0/script-reference/unityengine/rigidbody2d/mass.md) can be set.