The hurdle and runner form a right triangle (see attached picture) such that
sin(30°) = h / (5 ft)
and
cos(30°) = x / (5 ft)
where h is the height of the hurdle and x is the horizontal distance from where the runner jumps to the hurdle. So
h = (5 ft) sin(30°) = 5/2 ft = 2.5 ft
x = (5 ft) cos(30°) = (5√3)/2 ft ≈ 4.33 ft
