physics
posted by andrew .
A person standing at the edge of a seaside cliff kicks a stone over the edge with a speed of vi = 11 m/s. The cliff is h = 55 m above the water's surface, as shown below.
How long does it take for the stone to fall to the water?

The initial speed, which is horizontal, does not matter. You only need to solve the equation for vertical motion.
55 m = (g/2) t^2 = 4.9 t^2