Hello @hazingo,
if I just look at your equation, anything that looks like this x = b * x + (1-b) * y is a process of doing an exponential moving average (EMA) that updates x with y. The EMA is like a weighted sum, so if b = 0.85, then 85% of the next x comes from the current x and the rest 1-b =15\% from the new y value.
As b is higher, such weighted sum makes x to change slower to the new value y, because a higher b preserves more of the current x. Such ability of “preserving” makes it momentum-like.
If you still have questions or you think my answer isn’t what you are looking for, let me know, and also it would be great if you can share the reference to where you saw the equation, which video or which assignment?
Cheers,
Raymond