# In Physics, students are exploring forces through experimentation and on paper.

*Take a wine cork. Push a toothpick into one of the flat sides, and then push two forks at a shallow angle opposite each other along the curved side, with the handle of the forks on the same side as the toothpick. Do you think it will balance on the tip of the toothpick?*

Our students this block have been exploring the idea of center of mass through the cork and fork toy and exploring conditions under which it will be stable. They have discovered that the center of mass doesn’t just have to lie inside a body, but can hang in mid-air, and where it hangs, remarkably, decides whether this toy is stable. They will later tie these ideas together in the study of oscillations and the pendulum and be able to make abstract analogies to other oscillating systems.

We spent the first part of the block discussing overarching physical conservation laws like momentum and energy, which tells us what happens before and after an interaction. The majority of this block has been delving into the details of interactions themselves, through Newton’s laws. The reason for discussing the larger physical principles is that they lead to Newton’s laws in a more natural way for the students. They have learned how only two of the four fundamental forces, gravity and electromagnetism, manifest themselves in the macroscopic world. The big shift from Aristotle’s ideas to Newton’s are happening as students approximate those microscopic forces to real world ones like tension, compression, spring forces, and friction, all due to electromagnetism, and the one fundamental force they get to work with firsthand, which is gravity.

During classwork, one particular problem about hanging weights on springs had challenged the students. A group that was working on the problem and discussing their reasoning found that the ultimate test did actually lie in an experiment. In the spirit of true experimentalists, they got together springs from the lab, improvised weights from a previous experiment, and put their ideas to the test! As they refined the apparatus with pulleys and variable springs, they found that their theoretical arguments indeed matched what the supreme court of physics decreed, which was an experimental confirmation.

Part of our journey into physics is learning a new language and using it effectively to solve problems. Along with the geometric and algebraic description of motion, the students are learning a new diagrammatic language called free body diagrams. This is a representation of forces and is a major step ahead in abstracting mathematical models using the tools of vector analysis. We will explore more intuitive aspects of these diagrams and understand their role in experiments in the coming weeks.

*-- Kaushik Basu*