Simple Machines and Their Types

Simple Machines and Their Types

Middle School

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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

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Work

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

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Machine

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

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Fulcrum

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

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Lever

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

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Inclined Plane

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

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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?

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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.

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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.

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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.

Multiple Choice

How do simple machines help you?

• They decrease the weight of objects.

• They increase the force you apply, allowing you to move heavier objects.

• They eliminate friction completely.

• They make objects move on their own without any force applied.

Simple Machine: The Lever

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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.

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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.

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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.

Multiple Choice

If you are using a pair of tweezers to pick up a splinter, where is the effort applied in relation to the fulcrum and the load? What class of lever is it?

• The effort is between the fulcrum and load; Class 3

• The fulcrum is between the effort and load; Class 1

• It is not a lever

• The load is between the fulcrum and effort; Class 2

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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.

Multiple Choice

Which simple machine is best described as a wheel attached to a rod that rotates with it, such as in a doorknob?

• A lever

• A pulley

• A wheel and axle

• A screw

Simple Machines: Inclined Plane, Wedge, and Screw

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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.

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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.

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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.

Multiple Choice

Which of these simple machines is essentially an inclined plane wrapped around a cylinder?

• A screw

• A pulley

• A wedge

• A lever

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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.

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Multiple Choice

A pair of scissors is considered a compound machine because it is made of which two simple machines?

• An inclined plane and a wheel and axle

• A lever and a wedge

• A lever and a pulley

• A screw and a pulley

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Common Misconceptions About Simple Machines

Misconception	Correction
Machines reduce the total amount of work.	Machines change how work is done, trading distance for less force.
All machines produce more force.	Some machines increase distance or change the direction of force.
A screw is completely different from an inclined plane.	A screw is an inclined plane wrapped around a cylinder.

Multiple Choice

How does the function of a Class 1 lever, like a see-saw, differ from a Class 3 lever, like a fishing rod, in terms of applying force?

• A Class 1 lever can only change the direction of force, while a Class 3 lever can only increase force.

• A Class 1 lever always multiplies force, while a Class 3 lever always multiplies distance.

• In a Class 1 lever the fulcrum is between the effort and load, while in a Class 3 the effort is between the fulcrum and load.

• There is no functional difference between a Class 1 and Class 3 lever.

Multiple Choice

Which statement best describes the relationship between an inclined plane and a wedge?

• An inclined plane is a sharper version of a wedge.

• A wedge is a type of inclined plane that is circular.

• A wedge is formed by placing two inclined planes back-to-back to create a sharp edge for splitting.

• There is no relationship between an inclined plane and a wedge.

Multiple Choice

A bicycle is a compound machine. Which list correctly identifies three simple machines found in a bicycle?

• Screw, Lever, Inclined Plane

• Wheels and Axles, Levers, and Pulleys

• Lever, Wedge, Screw

• Inclined Plane, Pulley, Wedge

Multiple Choice

To get a heavy box onto a truck, you could use a long ramp or a pulley. How does each machine make the work easier, and what is the trade-off for each?

• Both machines reduce the total amount of work required.

• The ramp increases force but requires less distance; the pulley increases distance but requires more force.

• The ramp reduces the force needed by increasing the distance; the pulley changes the direction of force, making it easier to pull down.

• The ramp and the pulley both make work easier by increasing the force applied to the box.

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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.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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