How Are Vertical Distances Calculated in Projectile Motion?

[salman213]

1. http://img214.imageshack.us/img214/2684/77965080tu2.jpg [/URL]



I get (a) part but for the last part to find the vertical distances can someone explain what is done here. This is the solution

let h be the vertical distance

h = y + xtan30

h= volt tan30 - 1/2gt^2

then they differentiate to find maximum (i get that part). I just don't understand how they came up with those equations for the h distance...

can anyone explain?

 

[mgb_phys]

One of the equations of motion s = ut + 1/2at^2
Where s is distance, u is initial velocity, a is accelaration.
If you only think about the vertical motion of the skier, what is the initial vertical velocity and what is the accelaration.