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Simple
Machines
Simple
Machines
Simple Machine: A device for overcoming
resistance at one point by applying force
at some other point.
Work : The force applied on an object
multiplied by the distance traveled
by the object.
Effort : The force needed by a
machine in order to accomplish
work on a load.
Load : The resistance or weight
sustained by a machine.
Mechanical Advantage (MA) : The
ratio of the output force (acting on a
load) produced by a machine to the
applied effort (the input force).
The Six Simple Machines
•
•
•
•
•
•
Inclined Plane
Wedge
Screw
Lever
Wheel and Axle
Pulley
The Six Simple Machines
Two general classes of simple machines.
• Those that operate in straight lines or
vectors.
– Inclined Plane
– Wedge
– Screw
• Those that operate by turning.
– Lever
– Pulley
– Wheel and Axle
Inclined Plane
1 ft.
This inclined plane has a mechanical advantage of 3.
Mechanical Advantage = Length / Height
MA = Length (3 ft.) divided by the height of the incline (1 ft.).
3/1=3
MA = 3
Inclined Plane
3 lb
1ft.
Force x Distance = Work
3 lb of force x 1 ft or distance = 3 ft-lb work
Inclined Plane
1 ft.
By using in inclined plane with a mechanical advantage of 3 the
amount of force required is reduced to one pound.
Inclined Plane
EXAMPLES
Wedge
A wedge is a movable inclined plane.
Wedge
1 ft.
Mechanical Advantage = Length / Width
MA = 3/1
MA = 3
50 lb
Wedge
4 in.
If the wedge to the right is
pushed downward 12 in. with a
50 lb force the result would be
a force on the material it is
driven into of three times that
or 150 lb. over one-third of the
distance, 4 in.
150 lb
12 in.
150 lb
Wedge
EXAMPLES
Screw
1 ft.
A screw is basically an inclined plane wrapped around a cylinder.
Screw
Screw
Screw
EXAMPLES
Lever
Effort
Load
3 lb
Fulcrum
A lever is a bar that pivots about a point called the fulcrum.
Lever
1 ft.
MA=Fulcrum to Effort / Fulcrum to Load
MA=3 / 1
MA=3
Lever
Lever
Effort
Load
Work = 1 lb x 3 ft = 3 ft lb
Work = 3 lb x 1 ft = 3 ft lb
Lever
Effort
Load
Work = 1 lb x 3 ft = 3 ft lb
Work = 3 lb x 1 ft = 3 ft lb
Lever
Effort
Load
Work = 1 lb x 3 ft = 3 ft lb
Work = 3 lb x 1 ft = 3 ft lb
Types of Levers
Effort
Load
Fulcrum
First Class
Effort and Load on opposite sides of the Fulcrum
Types of Levers
Fulcrum
First Class
Effort and Load on opposite sides of the Fulcrum
Types of Levers
First Class = See Saw
Types of Levers
Effort
Load
Fulcrum
Second Class
Effort and Fulcrum on opposite side of the Load
Types of Levers
1 lb
Effort
Load
4 lb
Fulcrum
Second Class
Effort and Fulcrum on opposite side of the Load
Types of Levers
Fulcrum
Second Class
Effort and Fulcrum on opposite side of the Load
Types of Levers
Fulcrum
Second Class
Effort and Fulcrum on opposite side of the Load
Types of Levers
Load
Effort
Fulcrum
Third Class
Fulcrum and Load on opposite side of the Effort
Types of Levers
4 lb
Effort
Load
1 lb
Fulcrum
Third Class
Fulcrum and Load on opposite side of the Effort
Types of Levers
Fulcrum
Third Class
Fulcrum and Load on opposite side of the Effort
Types of Levers
Effort
Load
Fulcrum
Third Class
Fulcrum and Load on opposite side of the Effort
Lever
EXAMPLES
Wheel and Axle
Effort
Load 6 lb
Wheel and Axle
Effort
Load 6 lb
Wheel and Axle
Effort
Load 6 lb
Wheel and Axle
MA=Wheel Diameter / Axle Diameter
Effort
MA=6 / 1
MA= 6
Load 6 lb
Wheel and Axle
1 lb
Effort
Load 6 lb
Wheel and Axle
EXAMPLES
Pulley
3 lb
Effort
Load 3 lb
Pulley
1
Load 3 lb
3 lb
Effort
Pulley
3 lb
Effort
Load 3 lb
Pulley
2
1
Effort
Start
Start
Load
Pulley
1 ½ lb
Effort
Load 3 lb
End
Start
Start
End
Pulley
1
2
3
4
1 lb
Effort
Load
4 lb
Pulley
1 lb
Effort
Load
4 lb
Pulley
Start
End
Start
End
Pulley
EXAMPLES
References:
Examples
Morrow, H.W. (1998). Statics and Strength of Materials,
Upper Saddle River, NJ: Prentice Hall
Spiegel, L. & Limbrunner, G. (year). Statics and Strength
of Materials-4th ed., Englewood, NJ: Prentice Hall
Door Image - j0403728.jpg; Keyboard and Mouse - j0341934.jpg; Robots Welding - j0401916.jpg; Arm - j0431692.jpg – www.office.microsoft.com/enus/clipart
Pulley Image - http://en.wikipedia.org/wiki/Image:PulleyShip.JPG
Crane Pulley Image - http://en.wikipedia.org/wiki/Image:Crane_pulley_4x.jpg
Wheelchair and ramp - http://www.riton.com.au/wheel%20chair%20%20ramp%2014.jpg
See Saw - http://en.wikipedia.org/wiki/Image:Seesaw-aa.jpg
Wrench - http://en.wikipedia.org/wiki/Image:Open_ended_spanner.jpg
Tractor and Auger - http://en.wikipedia.org/wiki/Image:Tractor_with_Auger_01.JPG
Drill and Screw - http://en.wikipedia.org/wiki/Image:Wood_screw.jpg
Spiral Staircase - http://en.wikipedia.org/wiki/Image:Cremona%2C_torrazzo_interno_02_scala_a_chiocciola.JPG
Locomotive - http://en.wikipedia.org/wiki/Image:462driving.jpg
Bicycle Wheel - http://en.wikipedia.org/wiki/Image:Bicycle_wheel.jpg
Gears - http://en.wikipedia.org/wiki/Image:Gears_large.jpg
Credits:
Writer: Tad A. Douce
Content Editor: Tad A. Douce
Production Work: Tad A. Douce