---
title: "init(mass:stiffness:damping:initialVelocity:)"
framework: uikit
role: symbol
role_heading: Initializer
path: "uikit/uispringtimingparameters/init(mass:stiffness:damping:initialvelocity:)"
---

# init(mass:stiffness:damping:initialVelocity:)

Creates a timing parameters object with the specified spring stiffness, mass, damping coefficient, and initial velocity.

## Declaration

```swift
init(mass: CGFloat, stiffness: CGFloat, damping: CGFloat, initialVelocity velocity: CGVector)
```

## Parameters

- `mass`: The effective mass of the animated property. This value must be greater than 0.
- `stiffness`: The spring stiffness coefficient. Higher values correspond to a stiffer spring that yields a greater amount of force for moving objects.
- `damping`: The damping force to apply to the spring’s motion. This value is used to compute the damping ratio.
- `velocity`: The target property’s initial rate of change at the start of the spring animation. If the target property doesn’t change, specify a vector with dx and dy components of 0. For details about how to calculate this velocity, see doc://com.apple.uikit/documentation/UIKit/UISpringTimingParameters/initialVelocity.

## Return Value

Return Value An initialized spring timing parameters object or nil if the object could not be created.

## Discussion

Discussion The damping ratio for the spring is computed from the formula damping / (2 * sqrt (stiffness * mass)).

## See Also

### Initializing a spring timing parameters object

- [init()](uikit/uispringtimingparameters/init().md)
- [init(dampingRatio:)](uikit/uispringtimingparameters/init(dampingratio:).md)
- [init(dampingRatio:initialVelocity:)](uikit/uispringtimingparameters/init(dampingratio:initialvelocity:).md)
- [init(coder:)](uikit/uispringtimingparameters/init(coder:).md)