Science Buddies: "Ask an Expert"

So, my final topic is due TOMORROW! I have until February to complete it. I thought that measuring the distance travelled by a soccer ball of varying sizes would be simple enough. However, in searching for ideas on how to create a "kicking machine" i'm coming up empty handed. I'd really prefer to use a stable machine as opposed to my own foot.

Any suggestions or ideas?

A lot depends on what hypothesis you are attempting to test.

Something as simple as a 2x4 about 20 inches long to represent the knee to heel with a 6 inch long piece screwed on to represent a foot might work.
A piece of 1/2 plywood as a base, another couple pices of 2x4 about 26 inches long spaced so that the "leg" swings between them and a 1/2 bolt about 8 inches long, a few washers for spacers, some paraffin wax to coat the inside of a hole in the leg at the knee and the bolt to act as a lubricant and you have a device that you can raise to horizontal and let go of to provide a consistent kick.

That kind of a very simple and safe apparatus won't be able to test some hypothesis, especially ones that require a more powerful kick.

Making a more powerful kicking device involves more safety risks. If you can adjust your hypothesis so that it can be tested by a very simple and relatively safe device, it will be a lot simpler to do the project.

I think for this project, a very simple machine will be good enough. I even contemplated using a ramp just so that the balls had equal velocity. As long as the force making them move is equal, I would think that should work.

Thank you for the ideas. If anyone has any other ideas, I'm certainly open to the possibilities!

Please post your proposed hypothesis. That will enable the experts to provide better guidance.

Craig_Bridge wrote:Please post your proposed hypothesis. That will enable the experts to provide better guidance.

Problem: How does the size of a soccer ball affect how far it will travel?

Hypothesis: If the ball is smaller, then it will go farther.

jrzewtx wrote:Hypothesis: If the ball is smaller, then it will go farther.

Your hypothesis has at least two deficiencies. It doesn't say anything about what is causing the ball to move and it doesn't say anything about what the ball is traveling through/on.

To illustrate why the mechanism that creates the motion is important along with what is along the travel path, consider the following:
If you set the balls on a ramp at rest and then release them, the more mass (weight) the ball has, the more potential energy it has which likely means you would disprove your hypothesis (assuming smaller is lighter).

If you use a simple kicking machine similar to what I described setup to launch at a 30 degree angle, the smaller mass and diameter ball may have a higher departure velocity, a lower air resistance, and travel in the air farther than a larger mass and diameter ball assuming the pressure inside and elasticity of the ball's surfaces are similar. But what happens when the balls start rolling on the ground? The larger ball will have a larger rolling radius combined with a larger mass might make it roll farther. This maybe a case where altering the departure angle might affect the total travel distance. If you define the distance measured in your hypothesis to be only up to the first ground contact, the results might be different.

The hypothesis came from a 12 year old kid who's only had one year of actual "science"! Hence the need to either prove or disprove. I see how the mechanics can drastically effect the results. We are in the middle of a relocation. All of our tools are in another state! I was looking for EASY way to go about this!! It's turning out to be a rather difficult project!

Hi, jrzewtx!

Great to see you're really into this project! I think that Craig_Bridge has suggested that you be a little more specific with your hypothesis. It doesn't hurt to explain why you believe a small ball will go farther than a big ball impacted by the same force. Is it a gut feeling or intuition? If so, what makes it intuitive to you? When other people see your project, they'll want to know your reasoning, so it's best to have it laid out now.

Also, I am not sure exactly what resources you have for this project, but I did find a template for a kicking machine that might be of some use to you: http://pbskids.org/designsquad/pdf/pare ... _unit4.pdf.

It doesn't quite follow the design of your project because it focuses on aiming a small ball into a cup, but maybe you could use the link for ideas on how to structure your own project based on what you want to find. Hope this helps!

Thank you! I think his reasoning is that a smaller object has less resistance and would therefore travel farther than a larger ball when the same "force" is put upon it. He's just now learning about work, force, etc. Just learned the scientific method. It's a work in progress.

I sent the pdf to my husband to see if it's something he can work with. Thank you so much! Science projects have changed a little since I was in 7th grade. I grew crystals!

No problem! I'm glad to hear that your son's learning very actively and putting a lot of effort into this! Also, if he has read anything that influenced his reasoning, ensure that he has a list of sources handy so that re-finding citations/references isn't a problem in the future. If he's already doing this, fantastic!

By the way, it is interesting to hear about the diversity of projects over the years! As long as students enjoy what they work on, then nothing's really changed.