To find the initial velocity of this, what do I need to do? Ignoring Air resistance and Air Friction: I have found t, the total time it takes to reach the water, and the height maximum point, when the Vi = 0. I am lost how to find the initial velocity. I have tried deltaX / = v t , trying: 16.05 / 2 (the current t) = 8.025m/s I have tried finding t for the triangle part I made only, being sqroot of (8.03/5). This makes the Vi = 12.6649m/s, which I think is too big of a number :| Finally, taking the total Xx distance, 13.9[total Xx]/2[original t]: I get Vi=6.95

That has to do with...? Also in this problem I get to assume gravity is 10m/s^2. I just care about my initial velocity. Gravity should not matter to find this... right?

he's diving, he obviously ain't gonna fly 8m high in the sky then hit a wall and fall straight into the water. it's a parabolic movement, the horizontal movement is constant, and the vertical is accelerated.

You said you already know how long it takes for him to hit the water, no? We'll call that t1. So then your initial velocity in the X direction = 13.9/t1. From there, you should be able to do trigonometry with the angle of the dive.

I said that too, but with the math it does not matter. I am ignoring air resistance and friction. For purposes of equations, I can assume he hits a wall, because I do not care about his Xy descent, as I already know the change in Xy. The 30* angle and unknown speed provided will make it a superhuman jump and his speed is going to be ridiculous.

you know (13.9 , -12) X=Vo*T*cos(a) Y=Vo*T*sin(a) -0.5GT² unless you prefer this: Y= - X²G/2Vo²cos²(a) + X tan(a) http://en.wikipedia.org/wiki/Projectile_motion

The correct solution is Vi=6,34 m/s Plug it back into the projectile motion formulae and all the numbers fit.