How to Calculate Ball Height at Specific Distances in Projectile Motion?

[weskerq8]

Homework Statement

A soccer player kicks the ball off the ground from a horizontal distance of 17 m in front of the
goal as shown in Figure 1. He kicks the ball with a speed of 14 ms-1 at an angle of 45o to the
horizontal.

http://img190.imageshack.us/img190/4143/fig.gif

(a) What is the maximum height reached by the ball?
(b) How far from the goal is the ball when it is at its maximum height?
(c) The cross bar of the goal is 2.64 m above the ground. Does the ball pass under the bar?
(d) Can the ball be intercepted by a second player located 10 m in front of the goal
assuming he does not travel horizontally and can reach no higher than 3 m above the
ground?

Homework Equations

Xf = Xi + Vix t
Vy = Viy - gt
yf - yi = Viy t - 1/2 g t^2

The Attempt at a Solution

I don't have problems with part A and B as i already worked them out. I just need help on how to work on part C and D as I don't have any clue near on how to approach them.

my answers for part A was 5.001
and for part B was 27

I just want to learn how not to get the solution. Thanks in advance

 

[CompuChip]

The last two questions are basically of the type: calculate the height of the ball at horizontal distance X.
What I would do then, is convert the horizontal distance to flight time t (using one of the formulas you quoted) and then plug that into one of your other formulas to get the height.