I'm implementing the scrolling behaviour of a touch screen UI but I'm too tired in the moment to wrap my mind around some supposedly trivial piece of math:
y (distance/velocity)
|********
| ******
| ****
| ***
| ***
| **
| **
| *
| *
-------------------------------- x (time)
f(x)->?
The UI is supposed to allow the user to drag and "throw" a view in any direction and to keep it scrolling for a while even after he releases the finger from the screen. It's sort of having a momentum that depends on how fast the user was dragging before he took off the finger.
So I have a starting velocity (v0) and every 20ms I scroll by a amount relative to the current velocity. With every scrolling iteration I lower the velocity a bit until it falls below a threshold when I stop it. It just doesn't look right when I decrement it by a fixed amount (linear), so I need to model a negative acceleration but fail to come up with a decent simple formula how to calculate the amount by which I have to lower the velocity in every iteration.
Update:
Thank you for your responses so far but I still didn't manage to derive a satisfying function from the feedback yet. I probably didn't describe the desired solution good enough, so I'll try to give a real world example that should illustrate what kind of calculation I would like to do:
Assume there is a certain car driving on a certain street and the driver hits the brakes to a max until the car comes to a halt. The driver does this with the same car on the same street multiple times but begins to brake at varying velocities. While the car is slowing down I want to be able to calculate the velocity it will have exactly one second later solely based on it's current velocity. For this calculation it shou