Can anyone help explain how to convert velocities to different co ordinate systems? I've always been shocking at converting between co ordinate systems as it is. I know that converting from Cartesian to Cylindrical for positions it is: r = sqrt(x^2 + y^2) theta = atan(y/x) z = z and back its: x = rcos(theta) y = rsin(theta) z = z However, I'm getting confused as to what it would be for velocities. What I've got so far is: vx = vtheta * sin(theta) * sign(y) vy = vtheta * cos(theta) * sign(-x) vz = vz Am I doing the right kind of thing or am I overcomplicating things? Any help would be greatly appreciated!!