Hi, my first post here. Right. Spent the past hour searching all over for a clear explanation. In Circular Motion, or in general, the force perpendicular to the velocity vector changes only the direction and not the magnitude. Why is that so? My reasoning against goes like this - please explain which of my statements is wrong. Assuming velocity to be along x-axis, force acting along y-axis : 1/ Force produces acceleration. 2/ Acceleration will create a velocity along y-axis (initially v in y =0) 3/ Resultant of v along x(constant) and v along y(accelerated) will have different direction AND magnitude. I've broken it into 3 statements, please tell me which part is wrong. Much appreciated, thanks!