In one class, we measured the following average times: third floor: ball above this level for t3 = 0.72 s second floor: ball above this level for t2 = 2.16 s first floor: ball above this level for t1 = 2.70 s basement: ball above this level for t0 = 3.40 s We can then compute half of each interval: that yields the time it takes the ball to fall from the peak of its trajectory to each floor: third floor: fall from peak in time T3 = 0.36 s second floor: fall from peak in time T2 = 1.08 s first floor: fall from peak in time T1 = 1.35 s basement: fall from peak in time T0 = 1.70 s The distance a ball falls from the peak during each half-time tells us the distance from the peak downwards to each floor: peak 0 m below peak third floor 0.64 m below peak = 5.08 above second floor second floor 5.72 m below peak = 3.21 above first floor first floor 8.93 m below peak = 5.23 above basement basement 14.16 m below peak If the ball were released from the basement floor's level, and fell back to that level, then it would spend 1.70 seconds falling from rest; its speed would then be 16.7 m/s upwards, initially, or downwards, just before it strikes the floor.