A ball is projected horizontally from the top of a hill with a velocity of 3meter per second. If it reaches the ground 5 seconds later, the height of the hill is
recall that s = 1/2 at^2
The horizontal speed has nothing to do with the problem which is entirely in the vertical plane.
h = Hi + Vi t + (1/2) a t^2
h = 0 at ground
Hi is unknown
Vi = 0
a = -9.81 m/s^2 approx on earth
so
0 = Hi - (1/2) 9.81 * 25
Hi = 123 meters high