Simple Machines

Simple MachinesSimple MachinesMatt Aufman and Steve Case

University of MississippiNSF NMGK-8

February 2006

Matt Aufman and Steve CaseUniversity of Mississippi

NSF NMGK-8February 2006

NSF North Mississippi GK8NSF North Mississippi GK8

Simple MachinesSimple Machines

• Have few or no moving parts

• Make work easier• Can be combined to

create complex machines

• Six simple machines: Lever, Inclined Plane, Wheel and Axle, Screw, Wedge, Pulley

• Have few or no moving parts

• Make work easier• Can be combined to

create complex machines

• Six simple machines: Lever, Inclined Plane, Wheel and Axle, Screw, Wedge, Pulley


LeverLever Has three parts to it:1)Fulcrum 2) the load3) the effortTrade off: must move lever

large distance to move load small distance

• There are 3 types of levers

Has three parts to it:1)Fulcrum 2) the load3) the effortTrade off: must move lever

large distance to move load small distance

• There are 3 types of levers


1st Class Lever1st Class Lever• The fulcrum is

located between the effort and the load

• Direction of force always changes

• Examples are scissors, pliers, and crowbars

• The fulcrum is located between the effort and the load

• Direction of force always changes

• Examples are scissors, pliers, and crowbars

Draw this picture:


2nd Class Lever2nd Class Lever• The resistance is

located between the fulcrum and the effort

• Direction of force does not change

• Examples include bottle openers and wheelbarrows

• The resistance is located between the fulcrum and the effort

• Direction of force does not change

• Examples include bottle openers and wheelbarrows

Draw this picture:


3rd Class Lever3rd Class Lever• The effort is

located between the fulcrum and the resistance

• Direction of force does not change, but a gain in speed always happens

• Examples include ice tongs, tweezers and shovels

• The effort is located between the fulcrum and the resistance

• Direction of force does not change, but a gain in speed always happens

• Examples include ice tongs, tweezers and shovels

Draw this picture:


Mechanical AdvantageMechanical Advantage• To do these tasks without a machine would be

difficult.• We know that a machine multiplies whatever

force put into it (so you can complete the task) :

- Using a screwdriver to turn a screw - Twisting a nail with pliers - Carrying a box up a ramp instead

of stairs• The amount that the machine multiplies that

force is the mechanical advantage of the machine

• Abbreviated MA

• To do these tasks without a machine would be difficult.

• We know that a machine multiplies whatever force put into it (so you can complete the task) :

- Using a screwdriver to turn a screw - Twisting a nail with pliers - Carrying a box up a ramp instead

of stairs• The amount that the machine multiplies that

force is the mechanical advantage of the machine

• Abbreviated MA


Mechanical Advantage: LeverMechanical Advantage: Lever

• What is the MA for the example?

•Distance from effort to fulcrum: 10 feet

• Distance from load to fulcrum: 5 feet

The answer is: MA = 10/5 = 2

M A = Effort Arm (effort to fulcrum)Load Arm (fulcrum to load)


Inclined PlanesInclined Planes• A slope or ramp that

goes from a lower to higher level

• Makes work easier by taking less force to lift something a certain distance

• Trade off: the distance the load must be moved would be greater than simply lifting it straight up

• A slope or ramp that goes from a lower to higher level

• Makes work easier by taking less force to lift something a certain distance

• Trade off: the distance the load must be moved would be greater than simply lifting it straight up


Mechanical Advantage: Inclined PlaneMechanical Advantage: Inclined Plane• The mechanical

advantage of an inclined plane is the length of the slope divided by the height of the plane, if effort is applied parallel to the slope

• Let’s say S = 15 feet, H = 3 feet

• The mechanical advantage of an inclined plane is the length of the slope divided by the height of the plane, if effort is applied parallel to the slope

• Let’s say S = 15 feet, H = 3 feet

MA =Length of SlopeHeight of Plane

MA =Length of SlopeHeight of Plane

So for our plane MA = 15 feet/3 feet = 5


Wheel and AxleWheel and Axle• A larger circular

wheel affixed to a smaller rigid rod at its center

• Used to translate force across horizontal distances (like a car)

• Trade off: the wheel must be rotated through a greater distance than the axle

• A larger circular wheel affixed to a smaller rigid rod at its center

• Used to translate force across horizontal distances (like a car)

• Trade off: the wheel must be rotated through a greater distance than the axle


Mechanical Advantage: Wheel and AxleMechanical Advantage: Wheel and Axle

So for our wheel and axle MA = 10”/2” = 5

So for our wheel and axle MA = 10”/2” = 5

2"

10"

2"

10"

MA =Radius of WheelRadius of AxleMA =

Radius of WheelRadius of Axle


ScrewScrew

• An inclined plane wrapped around a rod or cylinder

• Used to lift materials or bind things together

• An inclined plane wrapped around a rod or cylinder

• Used to lift materials or bind things together


Mechanical Advantage: Screw

Mechanical Advantage: Screw

So for our screwdriver

MA = 3.14”/0.1” = 31.4

So for our screwdriver

MA = 3.14”/0.1” = 31.4

Diam.=1"

10 threadsper inch

Diam.=1"

10 threadsper inch

Circumference = ∏ x 1” = 3.14”

Pitch = 1/10” = 0.1”

MA = Circumference of ScrewdriverPitch of ScrewMA = Circumference of ScrewdriverPitch of Screw


WedgeWedge• An inclined plane on

its side• Used to cut or force

material apart• Often used to split

lumber, hold cars in place, or hold materials together (nails)

• An inclined plane on its side

• Used to cut or force material apart

• Often used to split lumber, hold cars in place, or hold materials together (nails)


Mechanical Advantage: Wedge

Mechanical Advantage: Wedge

• So for our wedge, MA = 6”/2” = 3• They are one of the

least efficient simple machines

• So for our wedge, MA = 6”/2” = 3• They are one of the

least efficient simple machines

2"

6"

2"

6"

MA = Length of SlopeThickness of Widest End

MA = Length of SlopeThickness of Widest End


PulleyPulley• A rope or chain free to turn

around a suspended wheel

• By pulling down on the rope, a load can be lifted with less force

• Trade off: no real trade off here; the secret is that the pulley lets you work with gravity so you add the force of your own weight to the rope

• A rope or chain free to turn around a suspended wheel

• By pulling down on the rope, a load can be lifted with less force

• Trade off: no real trade off here; the secret is that the pulley lets you work with gravity so you add the force of your own weight to the rope


Mechanical Advantage: Pulley

Mechanical Advantage: Pulley

• The Mechanical Advantage of a pulley is equal to the number of ropes supporting the pulley

• So for the pulley system shown there are 3 ropes supporting the bottom pulley

MA = 3• This means that if

you pull with a force of 20 pounds you will lift an object weighing 60 pounds

• The Mechanical Advantage of a pulley is equal to the number of ropes supporting the pulley

• So for the pulley system shown there are 3 ropes supporting the bottom pulley

MA = 3• This means that if

you pull with a force of 20 pounds you will lift an object weighing 60 pounds


The trick is WORKThe trick is WORK• Simple machines change the amount of

force needed, but they do not change the amount of work done

• What is work?•Work equals force times distance•W = F x d

• By increasing the distance, you can decrease the force and still do the same amount of work

• HW: Apr. 17 th (Thursday): Extra Credit:• Find a simple machine at home and

determine the mechanical advantage.

• Simple machines change the amount of force needed, but they do not change the amount of work done

• What is work?•Work equals force times distance•W = F x d

• By increasing the distance, you can decrease the force and still do the same amount of work

• HW: Apr. 17 th (Thursday): Extra Credit:• Find a simple machine at home and

determine the mechanical advantage.


Eduardo is helping his family move out of their old house. Help him decide which task would be easier, and then help him figure out what

simple machine makes the job easier.

Eduardo is helping his family move out of their old house. Help him decide which task would be easier, and then help him figure out what

simple machine makes the job easier.


Eduardo has to move some heavy boxes into the moving

truck.

Eduardo has to move some heavy boxes into the moving

truck.

A B

He would use an Inclined Plane


Eduardo has to move a heavy box a long distance.

Eduardo has to move a heavy box a long distance.

A B

He would use a cart with wheels and axles.


Eduardo needs to tear off a piece of packing tape.

Eduardo needs to tear off a piece of packing tape.

A B

He would use a scissors or wedges.


Eduardo needs to move a heavy box to his room on the fourth floor.

Eduardo needs to move a heavy box to his room on the fourth floor.

A B

He would use a pulley


Eduardo needs to help his father move the refrigerator.

Eduardo needs to help his father move the refrigerator.

He would use a lever

BA


Eduardo needs to help his father change a flat tire on the moving truck.

Eduardo needs to help his father change a flat tire on the moving truck.

A B

He would use a jack that uses a screw.


SourcesSourcesCOSI.org. 2006. Simple Machines. Accessed 3 February 2006. http://www.cosi.org/onlineExhibits/simpMach/sm1.html

Jones, Larry. January 2006. Science by Jones: Levers. Accessed 2 February 2006. http://www.sciencebyjones.com/secondclasslevers.htm

Mikids.com. 2006. Simple Machines. Accessed 2 February 2006. http://www.mikids.com/Smachines.htm

Professor Beaker’s Learning Labs. August 2004. Simple Machines: inclined planes. Accessed 2 February 2006. http://www.professorbeaker.com/planefact.html

Wikepedia. Accessed 3 February 2006. http://en.wikipedia.org/wiki/Mechanicaladvantage

http://www.cosi.org/onlineExhibits/simpMach/sm1.html

http://www.sciencebyjones.com/secondclasslevers.htm

http://www.mikids.com/Smachines.htm

http://www.professorbeaker.com/planefact.html

http://en.wikipedia.org/wiki/Mechanicaladvantage


Image SourcesImage Sources

<http://etc.usf.edu/clipart><http://www.oz.net/~peragine/doorknob.jpg><http://www.theteachersguide.com/clipart/scissors.gif><http://www.weprintcolor.com/stockimages/construction/

images/Black%20metal%20crowbar.jpg><http://67.19.222.106/military/graphics/flagpole.jpg><http://www.morris.umn.edu/UMMimages/public/images/

campus_misc/flagpole.jpg><http://www.phillips-screw.com/images/homeMain.jpg><http://mws.mcallen.isd.tenet.edu/mchi/ipc/ch15htm/

images15/Screw.jpg><http://www.discountramps.com/handi-van_ramp.gif>http://staff.harrisonburg.k12.va.us/~mwampole/1-resources/

simple-machines/flag-pole.jpg

<http://etc.usf.edu/clipart><http://www.oz.net/~peragine/doorknob.jpg><http://www.theteachersguide.com/clipart/scissors.gif><http://www.weprintcolor.com/stockimages/construction/

images/Black%20metal%20crowbar.jpg><http://67.19.222.106/military/graphics/flagpole.jpg><http://www.morris.umn.edu/UMMimages/public/images/

campus_misc/flagpole.jpg><http://www.phillips-screw.com/images/homeMain.jpg><http://mws.mcallen.isd.tenet.edu/mchi/ipc/ch15htm/

images15/Screw.jpg><http://www.discountramps.com/handi-van_ramp.gif>http://staff.harrisonburg.k12.va.us/~mwampole/1-resources/

simple-machines/flag-pole.jpg


Images Sources (cont.)Images Sources (cont.)

<http://www.physics.uwaterloo.ca/demo/bikewheelgyro.html>

<http://www.piratescave.co.uk/about_us.htm><http://staff.harrisonburg.k12.va.us/~mwampole/1-

resources/simple-machines/handicap-ramp.html><http://library.thinkquest.org/J002079F/

wedge.htm><http://www.idahoptv.org/dialogue4kids/season7/

simplemachines/facts.html><http://www.scienceclarified.com/Io-Ma/Machines-

Simple.html>

<http://www.physics.uwaterloo.ca/demo/bikewheelgyro.html>

<http://www.piratescave.co.uk/about_us.htm><http://staff.harrisonburg.k12.va.us/~mwampole/1-

resources/simple-machines/handicap-ramp.html><http://library.thinkquest.org/J002079F/

wedge.htm><http://www.idahoptv.org/dialogue4kids/season7/

simplemachines/facts.html><http://www.scienceclarified.com/Io-Ma/Machines-

Simple.html>

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