Well, there are no specific 'principles' that the physics community agrees upon, so the assignment is open-ended. I see two ways you could tackle it:
Option 1) There are fundamental theories:
1) Newtonian mechanics, which deals with the trajectories of baseballs and planets.
2) Quantum mechanics, which deals with the behavior of microscopic particles, e.g. those inside atoms.
3) Classical electromagnetism, which deals with antennas and cavity resonators and Maxwell's equations.
4) Special and general relativity, which together deal with relative motion and gravitation.
5) Quantum electrodynamics, which extends classical electromagnetism to the quantum domain.
6) Atomic theory and statistical mechanics, which deal with gases and ensembles.
7) Nuclear and particle physics, which deals with the particle zoo and modes of decay, etc.
You could do an outline of these 7 (or more) areas and the types of problems they solve. This would be, IMO, an excellent project on the 'principles of physics.'
Option 2) Another interpretation might be the principles of doing physics. These principles might be the mathematical and intuitive toolkit physicists use to solve problems. Such tools are the calculus (and all its subtypes, such as vector calculus, multivariable calculus, the calculus of variations, and differential equations), differential geometry, vector analysis, linear algebra, group theory, and so on. These topics unfortunately require a good bit of study (i.e. an undergraduate education or more) in order to accurately describe them. While it's a valid interpretation of the question, it'd be tough for you to do.
I say go with option 1!
- Warren