Hi JekiB,
Welcome to Science Buddies!
I think your child is interested in this excellent and fun project:
https://www.sciencebuddies.org/science- ... p099.shtml
Since this is for a science fair project, your child will need to do some type of experiment and measure results. The best project question is often the question that will be answered by the experiment. In the balloon-powered experiment, the objective is to see how far the car will go on one balloon.
Your child could compare different car designs, different race surfaces, different wheel materials. or maybe different balloons. So the project question might be one of the following:
Which balloon-powered car design will go farther?
Which race surface is best for balloon-powered cars?
Which wheel type works best for balloon-powered cars?
Which balloon provides the most car power?
In each of these experiments, your child will measure the distance that the car goes in centimeters or meters and the results will be displayed on a graph. A bar graph works well for the data on this type of project.
For your information, the parameter that is changed in the experiment is the independent variable. the distance that the car travels is the dependent variable. For each experiment, everything else should be kept the same, as much as possible. It's always best to repeat experiments in duplicate or triplicate (or more).
For a complete science project, it is necessary to do just one carefully controlled experiment, so have your child decide what topic to investigate and think of the project question.
I hope this helps. Please do let us know if you have any additional questions.
Donna Hardy