posted by anne .
A ball is thrown vertically upward with a speed of +12.0 m/s.
How long does the ball take to hit the ground after it reaches its highest point?
What is its velocity when it returns to the level from which it started?
Well, the easy way is to say the average speed of the ball on the awy up is (12 + 0) / 2 = 6 m/s
Now how high did it go?
(1/2) m v^2 = m g h
144/2 = 9.8 h
h = 7.35 meters up
6 t = 7.35
t = 1.22 seconds
part 2 is trivial, same speed down as up but opposite direction, -12 m/s