Re: What size soccer ball travls the farthest?

The veracity of an experiment is determined by its method not its result. The best experiments hold a truth of their own that is based upon reproduction by other experimentors. Write out your method in detail and stick to it when performing the experiments. In this way, some other scientist can do the same things you did and verify (or refute) your results. This concept is called refutability and is basis of true scientific experimental research.

In your experiment of kicking soccer balls you might expect the smaller ball to go farther than the biggest ball, and the middle ball to be somewhere in between. However, experiments have variations and errors that come from inconsistencies in measurement or performance of the experiment. Repeatability and statistical analysis are required. Averaging distance and considering standard deviation are necessary in any experimental measure.

I answered a question a while ago on driving golf balls
golf club answer
The questioner wanted to know how different metals affect the final distance. I explained a simple experiment to measure the effect of using different makes and materials of clubs.

Here is what I recommend for the soccer kicking experiment:

1) define how you will measure distance (final distance until stop, until the ball hits the ground, or something)
2) Obtain many kickers
3) Do the experiments all at once if possible to avoid differences in weather, energy level of the participants, or difference in the pressure of the ball. You may want to periodically check the balls and adjust the air pressure to some predetermined level for each.
4) Repeat the kicks for each ball a lot of times to get a good average. Compare results on a kicker by kicker basis and as a sum of all kickers.
5) Plot your results on a scatter plot or histogram with the variables (kicker, distance, ball).

Finally, your results are your results. Don't doctor the results to conform to some preconceived idea. As I stated above, you may expect the smaller ball to go farther, but who knows for sure. Maybe the bigger ball is easier to kick or rolls farther.

Sincerely,

Tom "2 out of 3" Cull