Which of the following is an example of a simple machine?

• A. All of the above
• B. Lever
• C. Pulley
• D. Inclined plane

Answer: (A)

A simple machine is a basic device that changes the size or direction of a force with relatively few moving parts. Each of the listed items fits that idea: a lever is a rigid bar that pivots about a fulcrum to amplify force; a pulley uses a wheel and rope to change the direction of the applied force; and an inclined plane is a flat, tilted surface that lets you raise or lower a load with less effort. Because all of these are classic examples of simple machines, the option that includes all of them is the best choice.