-- The velocity of the ball when it plunks back into the thrower's hand
will be the same 8.0 m/s but directed downwards this time.
-- Gravity robs 9.8 m/s from upward velocity each second. The ball can only
stand this for (8.0 / 9.8) = 0.816 second (rounded) before it stops rising and
begins to fall.
The round trip, from the thrower's hand, to the peak of the arc, and back to his
hand, takes (0.816 x 2) = 1.633 second. (rounded)
