4.47. Pulley http://www.ck12.org
4.47 Pulley
- Describe the simple machine called a pulley.
- Compare and contrast the three basic types of pulleys.
- Explain how to determine the ideal mechanical advantage of a pulley.
This rusty iron wheel has a rope wrapped around it. The wheel and rope hang over a building. Together they make
up a type of machine called a pulley.
What Is a Pulley?
Apulleyis a simple machine that consists of a rope and grooved wheel. The rope fits into the groove in the wheel,
and pulling on the rope turns the wheel. Pulleys are generally used to lift objects, especially heavy objects. The
object lifted by a pulley is called the load. The force applied to the pulley is called the effort.
Q: Can you guess what the pulley pictured above is used for?
A: The pulley is used to lift heavy buckets full of water out of the well.
Types of Pulleys
Some pulleys are attached to a beam or other secure surface and remain fixed in place. They are called fixed pulleys.
Other pulleys are attached to the object being moved and are moveable themselves. They are called moveable
pulleys. Sometimes, fixed and moveable pulleys are used together. They make up a compound pulley. The three
types of pulleys are compared in theTable4.4. You can experiment with an interactive animation of compound
pulleys with various numbers of pulleys at this link: