---
title: "strength(to:duration:)"
framework: spritekit
role: symbol
role_heading: Type Method
path: "spritekit/skaction/strength(to:duration:)"
---

# strength(to:duration:)

Creates an action that animates a change of a physics field’s strength.

## Declaration

```swift
class func strength(to strength: Float, duration: TimeInterval) -> SKAction
```

## Parameters

- `strength`: The new strength for the field.
- `duration`: The duration of the animation.

## Return Value

Return Value A new action object.

## Discussion

Discussion When the action executes, the field node’s strength property animates from its current value to its new value. This action is not reversible; the reverse of this action has the same duration but does not do anything.

## See Also

### Animating Properties of a Node’s Physics Body

- [applyForce(_:duration:)](spritekit/skaction/applyforce(_:duration:).md)
- [applyTorque(_:duration:)](spritekit/skaction/applytorque(_:duration:).md)
- [applyForce(_:at:duration:)](spritekit/skaction/applyforce(_:at:duration:).md)
- [applyImpulse(_:duration:)](spritekit/skaction/applyimpulse(_:duration:).md)
- [applyAngularImpulse(_:duration:)](spritekit/skaction/applyangularimpulse(_:duration:).md)
- [applyImpulse(_:at:duration:)](spritekit/skaction/applyimpulse(_:at:duration:).md)
- [applyImpulse(_:duration:)](spritekit/skaction/applyimpulse(_:duration:).md)
- [changeCharge(to:duration:)](spritekit/skaction/changecharge(to:duration:).md)
- [changeCharge(by:duration:)](spritekit/skaction/changecharge(by:duration:).md)
- [changeMass(to:duration:)](spritekit/skaction/changemass(to:duration:).md)
- [changeMass(by:duration:)](spritekit/skaction/changemass(by:duration:).md)
- [strength(by:duration:)](spritekit/skaction/strength(by:duration:).md)
- [falloff(to:duration:)](spritekit/skaction/falloff(to:duration:).md)
- [falloff(by:duration:)](spritekit/skaction/falloff(by:duration:).md)