Pulley

By: Ali Lewis and Drew Johnson

What is a pulley?

A pulley is a wheel and an axel that is designed to support movement of a cable or belt along its circumference. Pulleys are used in a variety of ways to lift loads, apply forces, and to transmit power.

Flag Pole

A flag pole is very tall and humans cannot reach that high so the pulley system helps us get the flag to the top of the pole.

Drew's Home Pulley System

This pulley system helps his family lift heavy objects into their attic that they cannot carry.

Conveyer Belt

This consists of two or more pulleys with a continuous loop of material that rotates around them.

Elevator

The cables are attached to the elevator car and they are looped around a pulley to raise or lower the car.

Mechanical Advantage

A pulley makes lifting a heavy object easier because it reduces the effort required to lift it. Although lifting becomes easier, you pull a rope that travels a greater distance than the height you lift the object. The extra distance decreases your effort by giving you mechanical advantage. Mechanical advantage depends of the number of ropes the pulley has to increase mechanical advantage you need to increase the number of support ropes. If you have three ropes you get three times as much force by pulling out three times as much rope. To find mechanical advantage you divide force in or effort by force out or resistance.

Problem

A pulley is used to raise a car. The pulley's input force of 400N is needed to provide an output force of 16,000N. What is the mechanical advantage of this pulley?

AMA= force out(resistance)/ force in (effort)

AMA= 16,000/400

AMA= 40

How Elevators and Pulleys Work
Working pulley system.