Science Buddies: "Ask an Expert"

Most of my science fair ideas require me to build a model, and need to know what the criteria is for verifying the model's data.

Hey there!

Sounds like you have a lot of ideas and that's great! It would probably help us respond better if we had some more specifics about what kind of projects you are thinking about. What type of model are you are thinking of building? The more specific you can get, the more we can help

So my main idea right now is to test the shape of propellers on boats and see how that effects the speed of the boat. My science teacher asked me how would I validate the data collected because this is a model, not an actual boat.

Hi!

That's a very unique project idea! Can you tell me the question you're trying to answer with you projects? Then, if you have one, can you tell me your hypothesis?

Thanks!

Hi williamzhang0306,

In addition to the advice shared by the other Experts, I wanted to share my perspective on your question. You question (unless I'm misunderstanding it) boils down to, "How do you take results from small-scale models and apply them to the full-sized objects?" This question is a really important one for many engineers. For example, when engineers design new aircraft, they often test smaller models of the aircraft in wind tunnels before testing the full-sized aircraft. Because the physics that govern the way air flows are understood in great detail, the engineers can then use computer models and a branch of science called "fluid mechanics" to extrapolate the results of the small-scale test to a full-sized aircraft.

Similar tests are done with propeller models in tanks of water. The physics of how water moves around propellers and other objects is very well known (water flow is actually controlled by the same physics as air flow). Consequently, small-scale experiments can be extrapolated to full-sized objects quite accurately once certain adjustments have been made. If you want to know more about how these types of adjustments for scale are done, I'm happy to explain that in more detail. However, you could also explain that engineers use model-sized objects quite frequently to understand how full-size objects will behave. The following articles gives an example related to airplanes, but the same ideas can be applied to scale models of propellers as well.

http://www.explainthatstuff.com/windtunnel.html