Physical science, which is most often called physics, is a very interesting and exciting topic. For an individual who likes technical things and is a hands-on type of person, physics is an invaluable tool. Physics allows us to explain how engines work, both piston and gas turbine; how airplanes and helicopters fly; and countless other things related to the field of aviation and aerospace. In addition to allowing us to explain the operation of the things around us, it also allows us to quantify them. For example, through the use of physics we can explain what the concept of thrust means for a jet engine, and then follow it up by mathematically calculating the pounds of thrust being created.

Physics is the term applied to an area of knowledge regarding the basic and fundamental nature of matter and energy. It does not attempt to determine why matter and energy behave as they do in their relation to physical phenomena, but rather how they behave. The people who maintain and repair aircraft should have knowledge of basic physics, which is sometimes called the science of matter and energy.

Matter is the foundation, or the building blocks, for any discussion of physics. According to the dictionary, matter is what all things are made of; whatever occupies space, has mass, and is perceptible to the senses in some way. According to the Law of Conservation, matter cannot be created or destroyed, although it is possible to change its physical state. When liquid gasoline vaporizes and mixes with air, and then burns, it might seem that this piece of matter has disappeared and no longer exists. Although it no longer exists in the state of liquid gasoline, the matter still exists in the form of the gases given off by the burning fuel.

Mass is a measure of the quantity of matter in an object. In other words, how many molecules are in the object, how many atoms are in the object, or to be more specific, how many protons, neutrons, and electrons are in the object. The mass of an object does not change regardless of where you take it in the universe, or with a change of state. The only way to change the mass of an object is to add or take away atoms. Mathematically, mass can be stated as follows:

The acceleration due to gravity here on earth is 32.2 feet per second per second (32.2 fps/s). An object weighing 32.2 pounds (lb) here on earth is said to have a mass of 1 slug. A slug is a quantity of mass that will accelerate at a rate of 1 ft. /s2 when a force of 1 pound is applied. In other words, under standard atmospheric condition, which is that gravity is equal to 32.2 fps/s, a mass of one slug would be equal to 32.2 lb.

Weight is a measure of the pull from gravity acting on the mass of an object. The more mass an object has, the more it will weigh under the earth’s force of gravity. The only way for an object to be weightless is for gravity to go away, because it is not possible for the mass of an object to disappear. When we view astronauts on the space shuttle, it appears that they are weightless. Even though the shuttle is far from the surface of the earth, the force of gravity has not completely gone away, and the astronauts are not weightless. The astronauts and the space shuttle are actually in a state of free fall, so relative to the shuttle the astronauts appear to be weightless. Mathematically, weight can be stated as follows:

Attraction is mutual force acting between particles of matter, which tends to draw them together. Sir Isaac Newton called this the “Law of Universal Gravitation.” Newton showed how each particle of matter attracts every other particle, how people are bound to the earth, and how the planets are attracted in the solar system.

Porosity means having pores or spaces where smaller particles may fit when a mixture takes place. This is sometimes referred to as granular—consisting or appearing to consist of small grains or granules.

Impenetrability means that no two objects can occupy the same place at the same time. Thus, two portions of matter cannot at the same time occupy the same space.

The density of a substance is its weight per unit volume. The unit volume selected for use in the English system of measurement is 1 cubic foot (ft3). In the metric system, it is 1 cubic centimeter (cm3). Therefore, density is expressed in pounds per cubic foot (lb⁄ft3) or in grams per cubic centimeter (g⁄cm3).