Simple Machines and Mechanical Advantage
Simple machines are devices that make work easier by changing the size or direction of a force. The six types of simple machines include levers, pulleys, wheels and axles, inclined planes, wedges, and screws.
What You Need to Know
Key Concept Diagram
Work = force x distance; simple machines allow the same work to be done with less force over a greater distance
A lever uses a fulcrum (pivot point) to amplify force: the longer the effort arm, the less force needed
A pulley changes the direction of a force; multiple pulleys reduce the force needed to lift heavy loads
Mechanical advantage = load force / effort force; a mechanical advantage greater than 1 means less effort is needed
Key Vocabulary
Simple machine
A device that changes the size or direction of a force to make work easier
Lever
A rigid bar that pivots around a fixed point (fulcrum) to lift or move loads
Fulcrum
The fixed pivot point around which a lever rotates
Mechanical advantage
The ratio of load force to effort force; shows how much a machine multiplies force
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
A lever has a load of 100 N and an effort of 25 N. What is the mechanical advantage?
Question 2
Moving the fulcrum closer to the load on a lever will:
Question 3
Which simple machine is used when you use a ramp to wheel a heavy object into a van?
Key Concepts Summary
- ●Work = force x distance; simple machines allow the same work to be done with less force over a greater distance
- ●A lever uses a fulcrum (pivot point) to amplify force: the longer the effort arm, the less force needed
- ●A pulley changes the direction of a force; multiple pulleys reduce the force needed to lift heavy loads
- ●Mechanical advantage = load force / effort force; a mechanical advantage greater than 1 means less effort is needed