I'm trying to build a tennis ball machine and I'm using a couple resources to help me out. One of them has the following formula for calculating drag force which I am having trouble interpreting.
The main question I have is what the V with a bar means and the difference between it and the regular V. I am also wondering if there is a special formula for calculating translational velocity. Any help would be much appreciated, and I'm not sure if it helps but cd is given as anywhere between .55 and .85. The air density could be 1.1376kg/m^3 and the radius of a tennis ball is around 3.35cm.
Thanks for your time and help!