Suppose a soccer player kicks the ball from a distance 15 m toward the goal. Find the initial speed of the ball if it just passes over the goal, 2.4 m above the ground, given the initial direction to be 35° above the horizontal.

Answer 1

height @ 15 m is 2.4m
h=vi*sin35*timeinAir -4.9 timeinAir^2=2.4
and...
15=vi*cos35*timeinAir or timinair=15/(vi*cos35) Putting that into first equation...
2.4=vi*sin35*15/(vi*cos35) - 4.9*(15/vi*cox35)^2
2.4=15*tan35 -4.9*(15/vi*cox35)^2 and you can solve that for vi with a tad of algebra.