Learning Objectives

• Define a simple machine and explain how it helps to make work easier.

• List and describe the six different types of simple machines found in everyday life.

• Explain the differences between the three classes of levers using effort, load, and fulcrum.

• Define a compound machine and identify the simple machines that make it up.

Key Vocabulary

Work

Work is the result of a force that successfully moves an object over a certain distance.

Machine

A machine is any device that makes doing work easier by changing a force's size or direction.

Fulcrum

The fulcrum is the specific fixed point around which a lever is able to pivot or turn.

Lever

A lever is a simple machine consisting of a rigid bar that pivots around a fixed fulcrum.

Inclined Plane

An inclined plane is a flat, sloping surface, like a ramp, that makes moving objects easier.

Compound Machine

A compound machine is a device made up of two or more simple machines working together.

What Are Machines and How Do They Help?

Increase the Force

• ​Machines can make you stronger by increasing the force you apply.

• ​​A small push on a lever can lift a very heavy object.

• ​This helps you move things you couldn't move on your own.

Change the Direction

• ​Some machines change the direction of the force you need to apply.

• ​​Using a pulley, you pull down on a rope to lift something up.

• ​This can make lifting objects to a higher place much easier.

Increase the Distance

• ​Machines spread force out over a longer distance to help you.

• ​​Pushing a box up a long ramp is easier than lifting it straight up.

• ​The amount of work stays the same, but the effort feels less.

Simple Machine: The Lever

Class 1 Lever

• ​The fulcrum is located between the effort and the load.

• ​​An example of this type of lever is a see-saw.

• ​A pair of scissors is another example of a Class 1 lever.

Class 2 Lever

• ​The load is positioned between the fulcrum and the effort.

• ​​A wheelbarrow is a common example of a Class 2 lever.

• ​You can also find this lever in a simple bottle opener.

Class 3 Lever

• ​The effort is applied between the fulcrum and the load.

• ​​A fishing rod is a great example of a Class 3 lever.

• ​A pair of tweezers also works as this type of lever.

Simple Machines: Wheel & Axle and Pulley

Wheel & Axle

• A wheel is attached to a smaller rod called an axle, and they rotate together.

• Force applied to the wheel or axle causes rotation to move objects or apply force.

• Examples include doorknobs, windmills, and car wheels.

Pulley

• A pulley is a grooved wheel that turns around an axle, used with a rope.

• It helps lift objects by changing the direction of the force applied to the rope.

• Pulleys are found in flagpoles, elevators, and wells.

Simple Machines: Inclined Plane, Wedge, and Screw

Inclined Plane

• An inclined plane is a flat, sloping surface, also known as a ramp.

• It makes moving an object to a different height much easier.

• A common example of an inclined plane is a simple ladder.

Wedge

• A wedge is made of two inclined planes that form a sharp edge.

• It is commonly used to split, cut, or pry different objects apart.

• An axe and a knife are everyday examples of a simple wedge.

Screw

• A screw is an inclined plane wrapped in a spiral around a cylinder.

• It is often used for holding objects together or for lifting things.

• The base of a common light bulb is an example of a screw.

What Are Compound Machines?

• A compound machine combines two or more simple machines to work together.

• ​They can perform more complex tasks than a single simple machine.

• For example, scissors use levers (handles) and wedges (blades).

• A bicycle uses wheels and axles, levers, and pulleys to move.

Common Misconceptions About Simple Machines

Summary

• Simple machines make work easier by changing the amount of force or distance.

• The six simple machines include the lever, pulley, wheel and axle, wedge, screw, and inclined plane.

• Levers are sorted into three classes, while wedges and screws are types of inclined planes.

• Compound machines are made by combining two or more simple machines to work together.