How to calculate the velocity of a moving object in a video or image sequence?

Hello I'm doing a master thesis on Leidefrost drops and I have several videos where a drop moves across a surface horizontally. I need to calculate its velocity and aceleration and I have no idea how. The only thing I have is code to track it using this: http://www.mathworks.com/help/vision/examples/motion-based-multiple-object-tracking.html I've attached a gif of the drop moving so you have an idea of what I'm asking.

Answer 1

[Walter Roberson]

Velocity = distance centroid moved divided by time interval.

You might find some useful techniques in https://www.mathworks.com/matlabcentral/answers/340746-how-to-count-number-of-car-passing-through-virtual-line-when-centroid-is-already-calculated#answer_267420 . For acceleration you would have to record the velocity as well as the position; either that or record the position for two previous generations.