Scissors are compound machines because they contain both a wedge and a lever. Bikes contain pulleys, screws, levers, wheels, axles and inclined planes.
A simple machine is a device or mechanism that changes force. Levers are simple machines that output force from a pivoting point. There are three kinds of levers used in simple and compound machines. They are hammer-type, wheelbarrow type and arm.
Pulleys are another simple machine used to make compound machines. Pulleys work by changing force due to the rotation of a pulley wheel. The wheel and axle is also a simple machine that is simply a pulley attached to a shaft. A car steering wheel and a Ferris wheel are good examples of wheel and axles.
Inclined planes redirect and redistribute horizontal force into vertical force and a wedge is two inclined planes which are back to back. Screws are used in compound machines and are merely inclined planes wrapped around a small cylinder. All of these simple machines can go into making compound machines. Some compound machines only use two while others use a variety of simple machines.Learn more about Motion & Mechanics