I need to find the initial velocity of a trebuchet launch. Data I have is a distance travelled of 11.1 m, time of 1.25 seconds, height of the sling straight up at 1.85 m. Equations I can use are V2 = V1 + a(t) , dy = V1(t) + 1/2(ay)(t)^2 , V2^2 = V1^2 + 2ad and viy = dy / t. Finding the initial horizontal velocity was simple using vix = dx / t and I ended up with 8.88 m/s. I know that the acceleration of y is 9.8 m/s^2 and so I think that I'm leaning towards one of the first three equations. Here's where I get stuck; I don't know which one to use because all of them have two variables that are missing. Also I'm not sure whether the maximum height of the sling off the ground will help me at all. I think that I'll be able to solve this problem if I can just figure out this initial y velocity. Any help would be greatly appreciated.