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# ThrowPropsPlugin.calculateChange()

ThrowPropsPlugin.calculateChange( velocity:Number, ease:*, duration:Number, checkPoint:Number ) : Number

[static] Determines the amount of change given a particular velocity, an easing equation, and the duration that the tween will last.

## velocity: Number

The initial velocity

## ease: *

The easing equation (like `Strong.easeOut` or `Power2.easeOut`).

## duration: Number

The duration (in seconds) of the tween

## checkPoint: Number

(default = `0.05`) — A value between 0 and 1 (typically 0.05) that is used to measure an easing equation’s initial strength. The goal is for the value to have moved at the initial velocity through that point in the ease. So 0.05 represents 5%. If the initial velocity is 500, for example, and the ease is `Strong.easeOut` and `checkpoint` is 0.05, it will measure 5% into that ease and plot the position that would represent where the value would be if it was moving 500 units per second for the first 5% of the tween. If you notice that your tween appears to start off too fast or too slow, try adjusting the `checkpoint` higher or lower slightly. Typically 0.05 works great.

### Returns : Number

The amount of change (can be positive or negative based on the velocity)

#### Details

Determines the amount of change given a particular velocity, an easing equation, and the duration that the tween will last. This is useful for plotting the resting position of an object that starts out at a certain velocity and decelerates based on an ease (like `Strong.easeOut`).