Machine Any arrangement of stationary and moving mechanical parts used to perform some useful Work or a specialized task. By means of a machine, a small Force can be applied to move a much greater resistance or load; the force, however, must be applied through a much greater distance than it would if it could move the load directly. The mechanical advantage of a machine is the factor by which it multiplies any applied force. The simplest machines are (1) the lever, consisting of a bar supported at some stationary point (the fulcrum) along its length, and used to overcome resistance at a second point by application of force at a third point; (2) the pulley, consisting of a wheel over which a rope, belt, chain, or cable runs; (3) the inclined plane, consisting of a sloping surface, whose purpose is to reduce the force that must be applied to raise a load; (4) the screw, consisting essentially of a solid cylinder around which an inclined plane winds spirally, whose purpose is to fasten one object to another, to lift a heavy object, or to move an object by a precise amount; and (5) the wheel and axle, consisting of a wheel mounted rigidly upon an axle or drum of smaller diameter, the wheel and axle having the same axis. The more complicated machines are merely combinations of these simple machines. Machines used to transform other forms of Energy (as Heat) into mechanical energy are known as engines, e.g., the Steam Engine or the Internal-Combustion Engine. The electric Motor transforms electrical energy into mechanical energy; its operation is the reverse of that of the electric Generator. In the past, the first machines, e.g., the catapult, were built to improve war-making capacity. The first manufacturing machines, powered by steam engines, appeared during the 18th century, causing the onset of the Industrial Revolution.