If I threw a ball off the roof of my house with a height of 5 m and the ball landed 20 m away, at what speed did I throw the ball?

Answer 1

Assuming you threw the ball horizontally (which is not stated in the problem), the time of flight is

t = √(2h/g)

Horizontal distance is

d = vt = v √(2h/g) ⇒

v = d / √(2h/g)

h = 5m

d = 20 m

g = 9.8 m/s²

Plug in the numbers and get v in m/s.