I am trying to find a method to calculate the velocity and acceleration of a tracked object, lets say a ball falling. I am using Processing 2 with the OpenCV library to make this program, and I know the distance from the camera to the object and it can calculate its position in every frame during the motion.
To calculate the velocity, I used this formula (all calculated in pixels): VelocityX=(PositionX - LastPositionX)/delta time
And something similar with acceleration: AccelerationX=(VelocityX - LastVelocityX)/delta time
Then, I changed delta time with frames. So now I have velocity and acceleration in Pixels per frame, but my question is how can I transform this Pixels per frame unit to mm/s for example? to more intuitive units like that.
I calculate the position in pixels too, but I make a conversion to mm after that, but I'm a little confused about how to do that for velocity and acceleration.