Test Corrections

^ represents the delta change sign because I don't know how to get a triangle

I don't have a blog of the kinematic equations or one about parabolic motions mainly because of confusion. At the time of learning, it's difficult to reflect and do a quality blog when I was confused because I had no idea what to write. But now that we have had a test, it's easier for me to reflect on this because there is something physical there, where I can explain what I did wrong and what I didn't understand.
So for number 15
The problem is
A diver running 3.6 m/s dives out horizontally from the edge of a vertical cliff and reaches the water below 2.5 s later
How high was the cliff?
What I did?
I tried using the a=^V/^t
And then I plugged in ^v in the 1/2a(^T)^2 +vi^T equation
which doesn't really make sense because initial velocity is definitely not the same thing as change in velocity. It is fair to assume that the initial velocity is 0, so you just plug the info you have into the change in position equation, and you would get out around 31 meters for your answer. 
How far from the base of the cliff did the diver hit the water? 
I can't even understand my work here and I don't know why I got it wrong. I feel like a lot of times with these problems I try to complicate it, and I think it possibly can't be that simple when it is. Basically, If you go 3.6 m/s and there are 2.5 seconds, you just multiply 3.6 by 2.5 and your answer is 9 meters.
17
A soccer ball is kicked from the ground and lands on the ground 2.2 seconds later
What is the initial vertical component of the ball's velocity
Once again I don't understand my work. But I overcomplicated it again,
Basically if you are trying to find the initial velocity, you can assume the position is 0, and then solve from there. You plug it into the the 1/2at^2 equation and your answer is around 11m/s
How high does the ball get above the ground
I didn't even answer this question, but since my vertical velocity was wrong this would be wrong too. Basically now you would plug in the vertical velocity in the equation and get out the change in position. But, you would need to use 1.1 seconds instead of 2.2, because 2.2 would give you the end results...since it is a parabola the maximum height would be at half the time.
If the ball was kicked at an angle of 55 degrees above horizontal, what was the balls total initial speed?
Once again, I got this wrong because I had the wrong vertical velocity. I did do the right process with the wrong velocity, but that doesn't matter. If i did the same thing, except using 11m/s, I would get the answer 13.4.
Basically, on a lot of problems, I mess up the process on one thing and then the rest of the problem is completely wrong. So i need to take my time and think what I am doing wrong.