Hi guys, I have some questions about this equation that my class were given before carrying out our practical for projectile motion (what we did was release a marble from the top of an inclined ramp and then when it hits the board which has a piece of carbon paper on it, a mark is left on a piece of paper under the carbon paper..) Here's the equation: y/x=[g(1+k^2)x]/2u^2 + k k is a constant g=gravitational acceleration y=vertical distance (between bottom of ramp and top of board) x=horizontal distance (between plumline and mark on paper) Questions: 1. What is k really? (I read from some other sites that k is air resistance. Is that true?) From what equation was it derived from? 2. How do I get this equation? What I've come up with so far..: y=(u sin Ɵ)t + 1/2 gt^2 x= u cos Ɵ t y/x= [(u sin Ɵ)t+1/2 gt^2]/(u cos Ɵ t) simplified it.. and I ended up with y/x= tan Ɵ + (gt^2)/(2u cos Ɵ t) So yeah, I'm stuck here. Help please? Not sure whether I'm on the right track..