What Is Physics and What Are Its Uses? Physics, a branch of science, is traditionally defined as the study of matter, energy, and the relation between them. The interaction between matter and energy is found everywhere. In order for matter to move, it requires some form of energy. Sports show many good examples of the relationship between matter and energy. For instance, a pitcher requires energy to throw a baseball at the incredible speed and accuracy that is needed to keep the batter from using his energy to try and hit the ball. The batter exhibits the need for a certain trajectory because he/she needs to