---
title: speed
framework: scenekit
role: symbol
role_heading: Instance Property
path: scenekit/scnphysicsworld/speed
---

# speed

The rate at which the simulation executes.

## Declaration

```swift
var speed: CGFloat { get set }
```

## Discussion

Discussion The default value is 1.0, which means that the simulation runs at normal speed. A value other than the default changes the rate at which time passes in the physics simulation. For example, a speed value of 2.0 indicates that time in the physics simulation passes twice as fast as the scene’s simulation time. A value of 0.0 pauses the physics simulation. note: Increasing the speed of the physics simulation reduces its accuracy.

## See Also

### Managing the Physics Simulation

- [gravity](scenekit/scnphysicsworld/gravity.md)
- [timeStep](scenekit/scnphysicsworld/timestep.md)
- [updateCollisionPairs()](scenekit/scnphysicsworld/updatecollisionpairs().md)