Alexis T. answered 05/06/20
Physics Degree Tutor
I think the easiest shortest solution is that you use a polynomial because it properly accounts for gravity and the motion of the ball, that is that there are two times it hits the same height, just that one had a positive velocity and the other time it has a negative one .
Because gravity is in the negative direction and your throw is in the positive direction, they will work against each other. That is until it hits a max height where velocity is zero and then the acceleration and velocity works with each other. This means a negative. The motion itself acts like a parabola so it only makes sense that the equation is going to be a parabola. An equation can mean something you visually see but put into mathematical syntax.