Kelsi and Sara are going to determine the height of tall building. Kelsi went to third floor hallway and measured the height of the window there to be 4.0 ft. Sara will drop a supper ball from the top of the building such that it will pass by the window. Kelsi starts a chronometer when she sees the ball at top of the window, reads the time as the ball passes the bottom of window. She reads 0.125s for this event, and does not stop the timer. The timer continues to run while the ball hits the side walk, bounces back and passes by the window again. Kelsi stops the chronometer as soon as she sees the ball arriving at bottom of the window. The timer reads 1.125 seconds.
Neglecting the air resistance, what do they calculate for the building height?
The Attempt at a Solution
not sure where to start