Science Buddies: "Ask an Expert"

I have a student that wants to find out which ball tennis or bouncy bounces the longest? I am having trouble deciding how to tell him how to accomplish this task. Also, I know that one is rubber and one fuzzy is this a variable?

Hi teachpsd,

Welcome to the board!

The output you're measuring (dependent variable) needs to be precisely defined. Do you mean "longest" as a measure of time?

The independent variable you can use is the type of ball, tennis vs. smooth rubber ball. I don't think you can use the characteristics of the surface as an independent variable, since the surface characteristics are fixed by the ball type.

For more information on variables please see:
https://www.sciencebuddies.org/science- ... bles.shtml
Thanks.

Hi David:

Thanks for the information. Actually I think the student wants to measure in height the longest, at least that is what he conveyed to me. Again, thanks for the infor.

Hi teachpsd,

if you'd like to measure how high the ball can bounce back, you'd want to make sure all the other variables are kept constant.

for example: the bounce surface material, height at which objects are dropped, method of dropping, method of measuring, etc.

in order to get accurate data, you should do at least three trials for each type of ball.

if you'd like to add some more experimentation to the project, i'd recommend how high the ball can bounce up on the 2nd, 3rd, etc. bounce instead of just the first.

-Dan

Height of bounces involve a change in kinetic energy which would somehow be related to MV*V / 2 and some elastic properties which involve surface radius and material properties. The one half mass times velocity squared is the kinetic energy equation for a point in time. This means that your different balls will likely have multiple different constituant properties (Mass and surface elasticity) that will affect your comparisons.

The bounce "frequency" and decay properties (how many bounces before it stops) will be less affected by mass and more affected by elasticity so it maybe easier to construct a meaningful hypothesis from one of those properties.

In any case, careful refined wording of a hypothesis so that it is measurable is going to be critical in terms of making this into a good Science Fair project.

Why is cycling in sports category instead of cars and transportation? I been using my bike for transportation for years and years. Most of the times gets me where I needed to go. There so many advatages using a bike over any motorize vehicle. But when it comes distances (100 miles) or carrying stuffs like a piano, it be another thing. I very seldom use it for sports.