Balloon powered car

[tdaly]

Hi Monadas,

The first thing to do is to make the graph. Then, look at the graph and see what patterns you notice. For example, does one car model go farther than another? Or faster than another? If so, which car goes farther (or faster)? If the graphs for both cars look similar, that's OK, too.

Remember that with an engineering design project, you need to specify design criteria (e.g., the car will go X meters in X amount of time while carrying X pennies). Alternatively, you could test how the number of pennies on a car affects how far and fast the car travels. Either option is OK. in the first option, you would need to adjust the design of your car until the data demonstrate that the car meets the design criteria. With the second option, you would make a distance vs. time graph for each car with a different number of pennies. For example, if you tested cars with 0 pennies 1 penny, 2 pennies, 4 pennies, and 8 pennies, you would have a total of ten distance vs. time graphs (car #1 with 0 pennies, car #1 with 1 penny, car #1 with 2 pennies, car #1 with 4 pennies, car #1 with 8 pennies, car #2 with 0 pennies, car #2 with 1 penny, car #2 with 2 pennies, car #2 with 4 pennies, and car #2 with 8 pennies). Choose whichever option you like best.

Now, if you already have distance vs. time data for your cars (and it sounds like you do), then I wouldn't worry about doing the things I described in the previous paragraph. But, I would analyze the distance vs. time graphs that you already have using the questions that I suggested in the first paragraph.

Post back as you have other questions!

[Monadas]

Hi, tdaly
I am using it the first way you said- "(e.g., the car will go X meters in X amount of time while carrying X pennies)."
So between my two car models: one with cardboard wheels weighing 4.6 g each and one with sprite bottle caps wheels that weigh 2.6 g each, the car with bottle caps wheels is going the farthest with the 19.85 g of pennies. (the diameter of cardboard wheel is bigger)

I also tested them without pennies but in that case the cardboard wheel car goes the farthest.:/

On the internet, I found that car with bigger wheels travels the farthest but when I test my cars ironically the car with sprite bottle cap wheels ( which is smaller than cardboard) go speedily and farthest with the pennies.

I don't know what to do. I want to use the one with bottle caps as the final design but I can't explain why its better than the cardboard one. I only have two points of explanation which is because the weight of the car with sprite bottle caps is lesser than the other one it is travelling faster with weights. And also because the sprite bottle caps are thicker.

Please help me explain more to this or suggest me something.

[Monadas]

And can I use a pressure gauge (one used to measure blood pressure) to measure the pressure in the balloon? I wanted to keep the same pressure in the balloon while doing the test.

[tdaly]

Hi Monadas,

I'm excited to hear that you have some results from testing your two cars! This is wonderful news!

It's OK that the Sprite car goes farther than the cardboard car when it has pennies on it, but that the cardboard car goes farther when there are no pennies involved. This is telling you that the weight of the cars makes a difference. Adding weight to either car will increase the friction force between the car's wheels and the floor. But, it will also change the friction forces between parts of the car itself (e.g., between the axles and the wheels). Depending on the design, the added weight could increase the friction forces among parts of the car by squishing them together. Alternatively, the added weight might push some parts of the car down more than others, which might free up parts of the car that were otherwise touching. Do the wheels of both cars spin the same with and without the weight? Or does the way (or ease with which) the wheels turn change as you add weight to the car?

One way to figure out what is causing you to get different results when they are tested within and without weights would be to look at the cars very carefully with and without the pennies weighing them down. Look for any differences in the way that parts of the car are touching or connected. The differences might be slight, so you'll need to observe carefully. Similarly, you can observe each car as it moves with and without weights on it and try to identify what's different in the ways that the wheels turn or that the parts of the car interact.

The fact that your results are different from what you read somewhere on the internet isn't particularly worrying in this case. Many design factors (besides the wheel size) could be at work and leading to different outcomes. The important thing is to follow your data. It sounds like the sprite bottle with weights is working better. If so, then use that as your final design. If someone asks you why you chose that as your final design, you can explain that the sprite car with pennies traveled farther than the cardboard car with pennies. Doing the careful observing that I talked out in the previous paragraph will help you understand why the sprite car with pennies is going farther.

I'm glad that you want to keep the pressure in the balloon the same in each test. That is an important controlled variable. Using a blood pressure cuff to measure the pressure in the balloon might work. You will need to watch for the pressure in the cuff at which the cuff just barely starts to compress the balloon. Then release pressure slowly until the balloon isn't compressed. The idea is that you want the pressure in the blood pressure cuff to exactly balance the pressure in the balloon. Then you can read the pressure off the blood pressure cuff.

Post back as you have other questions!

[Monadas]

Hi, tdaly,
Ok so I am using the sprite bottle car as my final design.
I realized that when weight is added the cardboard wheels take longer to rotate because of their diameter. It requires more force to accelerate a larger wheel. A small wheel is easier to spin with weights. Also the weight of the wheels/ car made a difference. The sprite car was 30 g and cardboard one was around 40. I can also explain in my explanation that smaller wheel would cost less which would relate to the problem I stated in my project.
So I am calculating time, speed and acceleration. Is there anything else I can calculate with the data I have??? Or is this much ok??

Again thank you for your explanation!

[Monadas]

And also what to put in the review of lierature part of the project report?
My report only has to contain a title page, table of contents, abstract, review of literature and citations.

[tdaly]

Hi Monadas,

I'm glad you were able to settle on a final design. The analysis that you've done sounds sufficient to me. But, you should definitely double check the instructions that your teacher gave you to make sure that you haven't missed something that your teacher asked you to include.

For your review of literature, you could talk about one-dimensional motions (kinematics), friction, and propulsion. You could also discuss some of the factors you chose to include as design criteria.

Post back as you have other questions. I won't be responding to posts tomorrow (Sunday), but I will be back again on Monday.

[Monadas]

Hi tdaly,
I just wanted to thank you for your guidance throughout the project! My presentation was good and your guidance was very much helpful.
Thank you

[terikdaly]

Hi Monadas,

You are very welcome. I'm glad to hear that your project turned out well!