For my experiment, I am doing experiment #6. So far I have constructed an apparatus that consists of one long track (60cm) and a 29.65cm track glued flat to it, with a 29.8cm track on the other end raised by 4 dominoes. I roll the large steel ball down the track and have it leave the track and hit a stationary small steel ball raised on a small platform that is 1.1cm tall and fall off of the table.
For my first data, I calculated that the balls both fell a vertical distance of 89.7cm. The large ball landed 15.7cm from the surface of the table. The small ball landed 28.3cm from the surface of the table.
Good.
It is unlikely that the centers of the two balls were at exactly the same height.
Most likely there was also some deviation in alignment so that at the instant of collision the centers were not quite aligned with the direction of motion of the first ball along the track; i.e., the center of the 'target' ball was probably a little left or a little right of the line of motion of the larger ball. This would result in the larger ball hitting the floor a little to the right or left of the target ball.
If you still have the original data, which consists of some marks on a piece of paper, check this out and let me know how closely you think the balls were aligned in the horizontal direction. If not, no problem, since you'll be taking a lot more data. Just be sure to observe this in future trials.
I believe the main goal of your experiment is to learn how the horizontal ranges of the two balls change as you change their relative height. As you start turning the screws You should therefore make your best effort to align the balls in the 'left-right' direction, and you should document this by measuring the 'left-right' deviations.
Another bit of 'base-line' data you will need for each height adjustment is the horizontal range of the first ball if it rolls down and off the ramp in the absence of the second ball. That horizontal range will be the distance from the 'straight-drop' landing position of the first ball, dropped from just below the point where it loses contact with the ramp. From that information you will be able to later determine the before-collision velocity of the first ball.
For your given data, assuming (not completely accurately) that immediately after both balls are traveling in the horizontal direction with no vertical component to the velocity of either, what are their after-collision velocities? You can answer this question by treating each as a projectile, having zero initial velocity in the vertical direction, for which you know the distance of the vertical fall and the horizontal range.