Question

Two tall buildings are 40m apart .with what speed must a ball be thrown horizontally from a window 145m above the ground in one building, so that it will enter a window 22.5m above the ground in other?

Answer 1

Difference in height = s = 145 - 22.5 = 122.5 m
From Newton's Equations of motion we know that:

s = ut +1/2 at²$s = ut + \frac{a t^{2} }{2}$  ...(i)

Using it along the vertical direction , we get
$=\ \textgreater \ 122.5 = \frac{g t^{2} }{2}$ ...(ii)


Using (i) in the horizontal direction we get:

40 = u t
=> $t = \frac{40}{u}$ ...(iii)
Solving equation (ii) and (iii), we get:

u = 8 m/s

Answer 2

For motion in the vertical direction  h==1/2 gt²

122.5=1/2 ×9.8×t²
245/9.8=t²
t²=25

t=5 s

For motion in the horizontal direction, 40 = ut and u = 8 m/s 

i hope its help you.