-- The acceleration of gravity is 9.8 m/s².
So if there's no air resistance, the speed of a falling object
always increases by 9.8 m/s for every second it falls.
Speed = (original speed) + (gravity x falling time)
-- If it has no vertical speed when it started, then at the end
of 3 seconds, its speed is
= (0) + (9.8 m/s² x 3 sec)
Velocity = 29.4 m/s downward .
