A tennis ball is thrown vertically upward with an initial velocity of 8.0 m/s. What will be its velocity when it returns to its starting point? How long will it take to reach its starting point?

-- 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 onlystand 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)