---
title: particleVelocity
framework: scenekit
role: symbol
role_heading: Instance Property
path: scenekit/scnparticlesystem/particlevelocity
---

# particleVelocity

The initial speed, in units per second, for newly spawned particles. Animatable.

## Declaration

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

## Discussion

Discussion Particles begin moving at this speed in the direction determined by the birthDirection or emittingDirection property. Their directions and speeds may change thereafter according to the acceleration property or physics effects (see the isAffectedByGravity, isAffectedByPhysicsFields, and colliderNodes properties). You can randomize the speed of newly spawned particles with the particleAngularVelocityVariation property. Particle speed is measured in units (of the local coordinate space containing the particle system) per second. The default value is 0.0 units per second, specifying that newly emitted particles are stationary until otherwise influenced. You can animate changes to this property’s value. See Animating SceneKit Content.

## See Also

### Managing Particle Motion

- [particleAngle](scenekit/scnparticlesystem/particleangle.md)
- [particleAngleVariation](scenekit/scnparticlesystem/particleanglevariation.md)
- [particleVelocityVariation](scenekit/scnparticlesystem/particlevelocityvariation.md)
- [particleAngularVelocity](scenekit/scnparticlesystem/particleangularvelocity.md)
- [particleAngularVelocityVariation](scenekit/scnparticlesystem/particleangularvelocityvariation.md)
- [particleLifeSpan](scenekit/scnparticlesystem/particlelifespan.md)
- [particleLifeSpanVariation](scenekit/scnparticlesystem/particlelifespanvariation.md)