posted by Diana .
A cannon is fired horizontally from a top of a 15-m platform. What is the cannon balls horizontal speed when it hits the ground 250 m downrange?
The time (t) that it takes to hit the ground is determined by the height above ground. For horizontal firing,
t = sqrt(2H/g) = 1.749 s
The horizontal speed must be (at all times)
250/1.749 = 143 m/s