The acceleration of gravity on Earth is about 9.8 m/s² .
That means that when anything falls near the surface of Earth,
its speed increases 9.8 m/s every second it falls.
If Superman falls for 7.8 seconds, then at the end of that time,
he's falling 76.4 m/s faster than he was at the beginning of it.
If Superman just kind of rolled off, so that he started with zero speed, then
at the end of 7.8 seconds, he would be falling at the rate of 76.4 m/s .
This is true not only of Superman, but of any falling object, such as
a rock, a flower pot, a lump of clay, etc.
It also makes no difference whether the fall began at the top of the
Eiffel Tower, the Empire State Building, the Petronas Towers, the
Burge Kalifa. or Niagara Falls.
