A machine is a device by which a small applied force can be multiplied to overcome a large resistive force or by which a gain of speed can be obtained. Some common applications of simple machines include lifting heavy loads by ack or pulley, riding a bicycle or cutting with a pair of scissors. Note: A machine cannot be used as a force multiplier and speed multiplier simultaneously.
Simple Machines - definition
Simple Machines : Simple machines are machines with few or no moving parts. They make work easier, user energy to work and change the direction of force. They include lever, screw, wheel and axle, inclined plane, pulley and wedge.
Complex Machines - definition
Complex Machines : Complex machines can be created by combining simple machines. They can be as small as a mechanical watch or as large as a construction crane. Complex machines are also called compound machines. Two or more simple machines work together to form a complex machine. Compound machines can do more difficult jobs than simple machines alone. Examples of complex machines are bicycle, wheel barrow, crane, car jack, lawn mover etc.