Lectures on Physics has been derived from Benjamin Crowell's Light and Matter series of free introductory textbooks on physics. See the editorial for more information....

# Simple Machines: The Pulley

Even the most complex machines, such as cars or pianos, are built out of certain basic units called simple machines. The following are some of the main functions of simple machines:

• transmitting a force: The chain on a bicycle transmits a force from the crank set to the rear wheel.
• changing the direction of a force: If you push down on a seesaw, the other end goes up.
• changing the speed and precision of motion: When you make the "come here" motion, your biceps only moves a couple of centimeters where it attaches to your forearm, but your arm moves much farther and more rapidly.
• changing the amount of force: A lever or pulley can be used to increase or decrease the amount of force.

You are now prepared to understand one-dimensional simple machines, of which the pulley is the main example.

 A pulley.

Last Update: 2009-06-21