SIMPLE MACHINES

Inclined planes, wedges, pulleys, wheels and axels, screws, levers and

compound machines

By: Cailyn Pacuraru, Claire Lippay and Pat McCarthy

Inclined Planes

• How it works• Why it’s useful• Mechanical advantage• References

Forward to Wedges

Definition

A plane set at an angle on a horizontal surface.

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How it Works

An inclined plane is a plane set at an angle on a horizontal surface. The inclined plane is a ramp that makes life easier by altering the amount of work that needs to be done. A steeper ramp requires more work, but it is a shorter distance to move the object.

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Why it’s Useful

The inclined plane is useful because it makes the work that needs to be done easier. You place the object on the plane and pull or push it up instead of carrying it the whole distance.

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How to Get the Mechanical Advantage

You can determine the mechanical advantage of an inclined plane by dividing the length of the incline by it’s height.

Ideal mechanical advantage =length of incline/height of incline

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References

• www.google.com (inclined planes)• www.jenkintown.org (under Mrs. Brooks’

website, 7th grade materials, simple machines)

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Wedges

• How it works• Why it’s useful• Mechanical advantage• References

Back to PlanesForward to levers

How it works

• It is a device that is thick on one end and tapers to a thin end on the other

• A wedge is a type of inclined plane. • The longer and thinner the wedge is, the less

input force is required to do the same work.

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Why it’s Useful

• It helps cut things in two or attach two things together.

• Example- a piece of wood: you cut it in two with a wedge, a zipper: you attach the two sides together or bring them apart.

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Mechanical Advantage

• The mechanical advantage can be found by dividing either slope by the thickness of the wedge.

Mechanical advantage=either slope/thickness

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References

• www.google.com (wedges)

• www.jenkintown.org (Under Mrs. Brooks’ website, 7th grade science materials, simple machines)

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Levers

• Types of levers• Mechanical advantage• Examples• References

Forward to screwsBack to wedges

Types of levers

• 1st class• 2nd class• 3rd class

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1st class levers

• In these levers, the distance from the fulcrum (the middle point) to the output force is less than to the fulcrum to the input force

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2nd class levers

• This type of lever always multiplies force, but not change the direction of the input force

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3rd class levers

• These levers multiply distance but do not change the direction of the input force

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Mechanical Advantage

• You can calculate the ideal mechanical advantage of a lever by using the distances between the forces and the fulcrum

Mechanical advantage=distance from fulcrum to input force/distance from fulcrum to output force

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Examples

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References

• Text book pages 118-128

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Screws

• What is it• Mechanical advantage • References

Forward to Pulleys Back to levers

What is it

• It can be thought of an inclined plane wrapped around a cylinder. You exert an input force on the screw when you twist it in something. As the threads of the screw turns, you put an output force on the object.

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Mechanical Advantage

• The closer together the threads of the screw are the greater the mechanical advantage

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References

• Text book pages 118-128

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Pulleys

• How it works• Mechanical Advantage

Forward to wheels and axels

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How it works• Pulley systems are used to lift large

masses onto tall heights. You might have seen workers repairing the roof of a house and using the pulley system to lift their tools or materials to the roof. A pulley is an example of a simple machine.

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Mechanical Advantage• The ideal mechanical advantage of a pulley

system is equal to the number of sections of the rope that support the object

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References• Text book pages 118-128

• www.capemaystudents.com

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Wheels and Axels• What is it• Mechanical Advantage• References

Back to PulleysForward to compound machines

What is it

• A wheel and axle is a lever that rotates in a circle around a center point or fulcrum. The larger wheel (or outside) rotates around the smaller wheel (axle).

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Mechanical advantage

• You can calculate the mechanical advantage of a wheel and axel using the radius of the wheel and the radius of the axel

Mechanical advantage=radius of wheel/radius of axel

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References

• Text book pages 118-128

• www.google.com

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Compound Machines

• What is it• Mechanical Advantage• References

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What is it

• A machine that utilizes two or more simple machines.

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Mechanical Advantage

You need to know the mechanical advantage of each simple machine used to get the mechanical advantage of a compound machine. The overall mechanical advantage is the product of the individual mechanical advantage of the simple machines.

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References

• Text book pages 118-128• www.google.com