3. A child throws a rock vertically upward from the edge at the top of a building with a speed of 5 m/s. There is a window with the top of its frame 2.5m below the child.

    A.    (12 points)

           What is the velocity of the rock at the top of the window?

                 Solution:

b.    (8 points)

If the rock takes 0.15s to travel past the window, how tall is the window? [Hint: it may be easier if you now set the origin at the top of the window for this part of the problem.

   Solution: