a ball is thrown horizontally from the roof o a building 78 meters tall and lands 65 meters from the base. what was the initial speed of the ball ?

Answer 1

Let's set the horizontal velocity as Vh and the vertical velocity as Vv. The horizontal displacement

d = V_h· t,

so we have

V_h=d / t.

where t is the traveling time both horizontally and vertically. So in the vertical direction, the free fall height h as the function of t is

h = 1/2 · g·t²,

so we have

t = sqrt(2h/g).

Now we have answer

V_h=d / t = d / sqrt(2h/g)

Plug in the values of d = 65, h=78 and g=9.8 into the equation above, you will get the value of V_h.