You can scroll on the bar or click the appropriate letter to find what you would like. Acceleration The rate of change velocity with respect to time. It is calculated by subtracting the initial or starting velocity from the final velocity and dividing the difference by the time required to reach that velocity. Achromatic An optical system that will transmit light without breaking it down into its component colors. Acoustics The science of the production, transmission, and effect of sound waves. Action The effect produced by a force, such as the force of a hammer hitting a nail: the action of the force is its effect, and the nail is driven into the wood. Adhesion The tendency for matter to cling to other types of matter, due to intermolecular forces. Adiabatic Pertaining to any activity that is not accompanied by a gain or loss of heat. Anode The positive terminal of an electrical current flow. In a vacuum tube, electrons flow from a cathode toward the anode. Bohr Theory A commonly accepted concept of the atom introduced by Niels Bohr in 1913. It holds that each atom consists of a small, dense, positively charged nucleus surrounded by negatively charged electrons that move in fixed, defined orbits about the nucleus, the total number of electrons normally balancing the total positive charge of particles in nucleus. Boyl's Law The principle that the volume of a gas times its pressure is constant at a fixed temperature. Cathode The negative terminal of an electric current system. In a vacuum tube, the filament serves as the cathode or source of electrons that are emitted. Conduction The transfer of heat by molecular motion from a source of high temperature to a region of lower temperature, tending toward a result of equalized temperatures. Convection The mechanical transfer of heated molecules of a gas or liquid from a source to another area, as when a room is warmed by the movement of air molecules heated by a radiator. Coulomb's Law The principle that an electro-static force of attraction or repulsion between electrical charges is directly proportional to the product of the electrical charges and inversely proportional to the square of the distance between them. Deceleration The decrease in velocity per unit time. It is also called negative acceleration. Density The mass per unit volume of a material. Every material has a characteristics density. Energy The ability or capacity to do work. There are numerous types of energy, including potential (stored), kinetic (from motion), heat, light, electrical, chemical, and nuclear energy. One form of energy can be transformed into another form, but energy normally is not created or destroyed. Entropy A physical quantity that is the measurement of the amount of disorder in a system. Equilibrium A state of balance between opposing forces or effects. Force The influence on a body that causes it to accelerate, as expressed by the formula F = ma, where F is force, m is mass, and a is acceleration. Friction The resistance to motion between two surfaces moving over each other. It is usually measured in terms of force and velocity. Heat A form of energy that results from the disordered motion of molecules. As the motion becomes more rapid and disordered, the amount of heat is increased. Kinetic Energy Energy that is associated with the motion of an object. Mass The measured amount of a material. All materials possess mass, and that mass never changes no matter where it resides in the universe. Mechanics A branch of physics that deals with the motion of objects. Medium The matter through which a wave travels. Sound waves need a medium; light waves do not need a medium and can travel through a vacuum. Particle Anything small and discrete, such as a proton, neutron, atom, or molecule. Phase The state of matter of a material-either solid, liquid, gas, or plasma. Physical Law A description of a certain behavior in nature; for example, the idea that an object does not change its position until it is acted on by an outside force is a physical law. Planck's Law Relates temperature to wavelength, starting that hotter objects radiate most at shorter wavelengths. Plasma A hot, ionized (electrically charged) gas. Potential Energy Energy that is stored because of position or configuration, such as the gravitational energy of a weight that is positioned on the roof of a building. Power The rate at which work is performed. Pressure The force acting on a per unit area of a surface. Radiation The emission and propagation of a radiant energy-either atomic, by radioactive substances, or spectral, as in light. Reaction The effect opposition of an action. A reaction is equal to an action but is in the opposite direction. For example, when a stone strikes a wall, the wall does not move or change shape-it pushes back with a reaction that is equal to the action. Resistance A force that opposes a change in motion or shape. Speed The distance traveled divided by the time it takes to travel the distance. Strain The change in a shape or size of a body caused by pressure and movement. Stress Tension forces exerted on a body that tends to produce a deformation of that body. Surface tension The property of a liquid in which the surface molecules show a strong inward attraction, forming an apparent membrane across the surface of the liquid. Thermodynamics The study of the movement of heat from one body to another and the relations between heat and other forms of energy. Vacuum In theory, it is the absence of matter; in space, a vacuum is where air or other gases are almost exhausted. Velocity The speed with which an object travels over a specified distance during a measured amount of time. Vibration The regulation oscillation, backward and forward, of a material. For example, elastic vibrates, as do most fluids. Viscosity The property of a liquid that makes it resist flow or any change in the arrangement of its molecules. The higher the viscosity, the "thicker" a liquid seems. Weight The force on a body produced by the downward pull of gravity on it. Work The force applied to an object times the distance over which it is applied. Work may be independent of the energy expended.     COPYRIGHT©2005 VICTORIA PACKING CORP. ALL RIGHTS RESERVED ( CTR-110505-PHY)