On Earth, the acceleration of gravity is 9.8 m/s² downward.
So any object with only gravity acting on it gains 9.8 m/s of
downward speed every second.
If the rock starts out moving upward at 10 m/s, then it will
continue upward for only (10/9.8) = 1.02 second, before
it stops rising and starts falling.
Its average speed during that time is (1/2) (10 + 0) = 5 m/s .
At an average speed of 5 m/s for 1.02 sec,
the rock rises
(5 m/s) x (1.02 sec) = 5.102 meters .
Krypton ... symbol Kr ... is an element. It's element number 36, because
there are 36 protons in the nucleus of every atom of Krypton.
Krypton has nothing to do with Superman, except that about 75 years ago,
the creators of Superman thought it was a cool-sounding scientific word,
so they chose it for the name of his home planet.
