I realise I may way out of my depth here.... but i thought i'd jump in anyway. so thats the question...is there a specific formula? feel free to call me an idiot if i've got this all wrong :P Cheers Tony EDIT: sorry, i forgot a bit of background.... so i'm doing a physics experiment revolving around modelling true golf ball trajectories. the magnus effect plays a pretty large role, and in my hpothesis, i'd like to create a formula factoring it in. EDIT2: ok, so i THINK i've found a formula... i dont know how everyone else gets the cool symbols, so im just going to use regular letters. sorry if its confusing... Fm = 2pi(p)(w)(vx)(h r^2) where p = density at 25 degrees C, w = angular velocity, vx - horizontal velocity and h r^2 = height of cylinder multiplied by the radius squared. this formula is for a cylinder. i've rearranged it: Fm = 2(p)(w)(vx)(pi r^2 h) now, as far as i can remember, pir^2h is the formula for the volume of a cylinder... as im looking at golf, i've taken out that formula and replaced it with the formula for the volume of a sphere: Fm = 2(p)(w)(vx)(4/3pi r^3) which eventually, returns the pi to the front: Fm = 8pi(p)(w)(vx)(r^3) 3 ^^ thats divided by 3, btw. ok, so is THIS is viable formula?