The experiment was to measure muzzle velocity of a ball fired by a 'spring gun'. Then to use the equations of projectile motion in order to determine the projectile trajectory. During the experiment we used a variable-height platform to stop the ball mid-air (at y = 0.4 m & y = 0.1 m). Now we're suppose to use the data to determine the final landing point of the trajectory. I have all my data, and I've created the projectile trajectory in excel from the initial position to y = 0.10 m. Now I'm lost on how to complete the trajectory!? The professor wants us to use the quadratic equation to solve for Xp (Xp is the final point of impact, where y = 0). But I don't know what information to plug into the quadratic equation. And even if I did, it doesn't make sense to me because the range should just be v0 * t. Can somebody please nudge me in the right direction? If I'm not explaining this clearly, please let me know and I'll post my lab data sheet. I just need to know how to complete this trajectory using the quadratic equation to solve for xp.