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. The term physics comes from a Greek word meaning nature. The subjects studied by physicists can be divided into seven main groups: (1) mechanics, (2) heat, (3) light, (4) electricity and magnetism, (5) solid state physics, (6) sound, (7) atomic and nuclear physics. Mechanics is the study of objects, forces, and motion, and such properties of matter as elasticity and weight. The principles of mechanics tell us the meaning of weight, mass, force, energy, space, time, and rotational motion. Sports show many good examples of the relationship between matter and energy. For instance, a pitcher requires energy to throw a
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 hit the ball hard enough and keep it high enough to sail over the outfield wall. On the other hand, the batter must be certain to keep the trajectory low enough so that the ball will reach the . Trajectory is also seen in basketball, where players must shoot the ball with enough arch to get over the front of the rim, and go through the hoop. The energy required to do this comes from not only the arms, but the legs as well. The study of light is called optics. It involves learning what light is, how it behaves, and how it can be used. A knowledge of how light behaves has helped in the development of instruments such as the microscope and the telescope. The medical field has seen enormous breakthroughs because of the principles of light.. Doctors are now able to use lasers for surgery. Lasers are devices for the creation and amplification of a narrow, intense beam of coherent light. New laser microsurgery can actually alter the shape of the cornea in the eye so the patient's eyesight can return to normal, and he/she will no longer need those bothersome glasses. The study of sound is called acoustics. It explains how sound is produced, transmitted, and reflected; and why it changes. Ultrasound is used in the medical field for destroying various unwanted substances in the body such as kidney stones. Ultrasound uses sound waves to dissolve these foreign bodies. If not for physics, ultrasounds would never have been discovered and utilized. Electricity and magnetism are closely related. Electricity can produce magnetism, and magnetism can produce electricity. An understanding of this important relationship has led to the development of many valuable inventions. In the field of medicine, MRI scans, are another new discovery based on the principle of electromagnetism and the phenomenon that nuclei of some atoms line up in the presence of an electromagnetic field. They are able to show a complete three dimensional picture of the interior structure of the body, and are extremely valuable in hospitals. The study of heat is called thermodynamics. Physicist study how heat can be changed into work, how it is produced, how it is transferred from one place to another, and how it changes matter. Heat ranks as one of the most important kinds of energy that is used. The knowledge that physicists gain from the study of heat and how it acts, aids in making use of heat energy to warm homes, cook foods, and run machines. Atomic and Nuclear Physics have revealed many of the secrets of matter. Knowledge gained from the study of nuclear physics has released the greatest energy known on earth, the energy of the atom. Solid State Physics supplied information that led to such developments as the transistor and the solar battery. It involves the study of the physical properties and atomic structure of solids, particularly of crystals. Physics is one of the most active and most important of all sciences. In laboratories throughout the world, physicists delve into the mysteries of nature to discover the secrets of the universe.