How about the physics of baseball? How much theoretic physics should a baseball player have to know? What physical choices does a batter have to make? Bat weight? Stance? The force behind hitting a low pitch vs. a high pitch? etc. etc. You could expand to the pitcher's physics -- the curve, the slider, etc. And finally you could discuss the ground ball bounce. The physical sciences deal with the laws of physics on the kinetic level, rather than the molecular or astronomical level. If time and space permit, you could deal with the air temperature at game time, or Summer game conditions vs. chilly October days.