Technology: Engineering Our World © 2012 Chapter 8: Machines—Glossary friction. A force that acts like a brake on moving objects. gear. A rotating wheel-like object with teeth around its rim used to transmit force to other gears with matching teeth. hydraulics. The study and technology of the characteristics of liquids at rest and in motion. inclined plane. A simple machine in the form of a sloping surface or ramp, used to move a load from one level to another. lever. A simple machine that consists of a bar and fulcrum (pivot point). Levers are used to increase force or decrease the effort needed to move a load. linkage. A system of levers used to transmit motion. lubrication. The application of a smooth or slippery substance between two objects to reduce friction. machine. A device that does some kind of work by changing or transmitting energy. mechanical advantage. In a simple machine, the ability to move a large resistance by applying a small effort. mechanism. A way of changing one kind of effort into another kind of effort. moment. The turning force acting on a lever; effort times the distance of the effort from the fulcrum. pneumatics. The study and technology of the characteristics of gases. power. The rate at which work is done or the rate at which energy is converted from one form to another or transferred from one place to another. pressure. The effort applied to a given area; effort divided by area. pulley. A simple machine in the form of a wheel with a groove around its rim to accept a rope, chain, or belt; it is used to lift heavy objects. screw. A simple machine that is an inclined plane wrapped in the form of a cylinder. torque. A measure of turning effort. velocity. The speed of an object; also the rate of change in an object’s motion. viscosity. The thickness of a liquid, caused by the friction of its molecules rubbing together. wedge. A simple machine that consists of two inclined planes placed back-to-back. wheel and axle. A simple machine that is a special kind of lever; effort applied to the outer edge of the wheel is transmitted through the axle. work. A measurement of the amount of effort needed to change one kind of energy into another. Copyright Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only..