How do I create this slide/bouncy effect in After Effects?
Key is creating 2 additional keyframes after the last one (one copy of the last one 5-10 frames ahead and another one in between). The keyframe in between is for shifting the position slightly into the opposite direction. In order to get a non linear animation ease all the keyframes at the end.        





Instructions


Create a new composition and a new solid layer with the dimensions of the gauge
Click the solid layer and create a mask (double click the rectangular mask path icon to create new mask with the dimensions of the solid layer)
Open up the mask properties of the solid / gauge layer MM
Go to the end of the composition and add a keyframe by clicking on the stop watch of the mask path property
Go to the first frame of the composition and drag both right mask bezier points to the left (this will automatically insert a new keyframe)
Copy the last keyframe 5-10 frames ahead and another one in between
With the cursor on the keyframe in between, drag both bezier points on the right side of the rectangle slightly to the left
Select the last 3 keyframes
Right Click > Keyframe Assistant > Easy Ease or simply hit F9


Examples

Bounce to the right



Bounce to the left 





Project File Download