The entire goal of the project is to DO SOME EXPERIMENTAL PHYSICS using your arduino and associated components.
This means we don't just want to make a little gadget type thing (i.e. an alarm clock, or Subway countdown timer, or Cat Food Dispenser ). Those are all fun and cool, but not really physics related.
To help clarify, consider some of the examples we looked at during the semester. We measured temperature as a function of time: $T(t)$ on several occasions. There are many different physical situations which can affect temperature. Some of them have well formed theoretical equations dictating what that function should look like (i.e. on a graph of $T$ vs. $t$). Doing physics in that case would be to set up an experiment that created one of these situations, measure the temperature, and see that your acquired data fit the expected theoretical predictions.
Or the one studied in PHYS 351: the pendulum attached to an oscillating support.
The Lagrangian of that system looked like: \begin{equation} L = T - U = \frac{1}{2}m \left(l^2 \dot{\theta}^2 + \dot{x}^2 + 2 l \dot{x} \dot{\theta} \cos \theta \right)+ mgl \cos \theta \end{equation} and produced an equation of motion given by: \begin{equation} l \ddot{\theta} - A \omega^2 \cos \left(\omega t \right) \cos \theta + g \sin \theta = 0 \end{equation}
Solving the equation of motion leads to the plot shown above. Now, could we build a version of this using simple toys and parts and then measure the angle as a function of time using the arduino? Yes. We could also make the arduino control the drive frequency $\omega$. We could then see how our results compared to the predictions. If they didn't, then maybe we need to improve our experiment. Or maybe the theory is wrong (doubtful). The we could write a few pages of text and explanation and equations and plots and then we'd have a project!
That's what is meant by doing physics here. Sure, you can make the arduino do all kinds of cool things that fall into the gadget category, and there are thousands of examples already out there. But, those are not really probing nature at all. They are product/industrial engineering. Sure, they involve physics, but what doesn't to some degree?
As I mentioned, there are more sensors than what came in your kits. I have this 37 sensor kit and you can borrow something from there if you can't procure one yourself.
So, you don't need to feel like your goal is to discover new physics. But rather, build something and measure things to confirm existing physics, while taking advantage of the data acquisition abilities of the mini-computers in the arduinos. (Their key strength is that that can measure thousands of data points quickly.)
Big overview: physics (and science) is a creative endeavor, just like being an artist, except with more math and usually better paychecks (though not always). At some point in the career of a physicist, no one tells you what to do any more and YOU have to come up with things to do. Consider this practice (with easier targets).
The basic idea is to try to follow the structure of a real scientific publication.
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