Download Simple Machines

Simple Machines
Guilford County Sci Vis
V205.07
Simple Machines
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Devices such as
levers, ramps, and
pulleys that make our
work easier.
They allow us to apply
effort at one place to
do work at another
point and/or to
change the direction
of a force.
Simple Machines
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One way is to magnify an
effort force so that a smaller
effort can be applied over a
longer distance thus moving
a large load a small
distance.
Examples:
 a crowbar being used to
dislodge a boulder,
 a nutcracker being used
to crack a nut,
 or a block tackle pulley
system being used to lift
a large weight.
Source:http://www.lakelandschools.org/EDTECH/Machines/RubeMain.jpg
Simple Machines
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The mechanical advantage of a
machine is the ratio of the load
force to the effort force.
The crowbar, nutcracker, and block
and tackle pulley system have a
mechanical advantage greater than
one.
Other machines have a mechanical
advantage less than one allowing
magnification of the distance and
speed of a movement.
An example of this might be a
fishing rod or baseball bat.
Simple Machines
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Inclined plane -- a sloping
surface, such as a ramp.
 An inclined plane can be
used to alter the effort and
distance involved in doing
work, such as lifting loads.
 The trade-off is that an
object must be moved a
longer distance than if it
was lifted straight up, but
Source: http://www.sirinet.net/~jgjohnso/inclineplanecolored.jpg
less force is needed.
 Examples: staircase, ramp,
and bottom of a bath tub
Simple Machines
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Wedge -- two inclined
planes joined back to
back.
 Wedges are used to
split things.
 Examples:
Axe
Zipper
Knife
Simple Machines
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Screw -- an inclined plane
wrapped around a shaft or
cylinder.
 This inclined plane allows the
screw to move itself or to
move an object or material
surrounding it when rotated.
 Examples:
Bolt
Spiral staircase
wood screw
Corkscrew
screws on light bulbs
Simple Machines
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Wheel and axle -- a wheel and axle has a larger
wheel (or wheels) connected by a smaller cylinder
(axle) and is fastened to the wheel so that they
turn together.
 When the axle is turned, the wheel moves a
greater distance than the axle, but less force is
needed to move it.
 The axle moves a shorter distance, but it takes
greater force to move it.
 Examples:
Door knob
Wagon
Toy car
Bicycle gears
Screw driver
Simple Machines
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Pulley -- a wheel that usually has a
groove around the outside edge.
 This groove is for a rope or belt to
move around the pulley.
 Pulling down on the rope can lift
an object attached to the rope.
 Work is made easier since pulling
down is assisted by gravity.
 Examples:
Flag pole
Crane
Source: http://www.edinformatics.com/math_science/simple_machines/pulley.htm
Elevators
Window blinds
Simple Machines
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Lever -- a straight rod or board that
pivots on a point known as a fulcrum.
 The fulcrum can be moved depending
on the weight of the object to be lifted
or the force you wish to exert.
 Pushing down on one end of a lever
results in the upward motion of the
opposite end of the fulcrum.
 Examples:
Door on hinges
Seesaw
Hammer
Bottle opener
Classes of Levers
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The class of a lever is
based on the relative
position of the load,
effort, and fulcrum.
Levers are classified
into 1st class, 2nd
class and 3rd class
levers.
Classes of Levers
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1st class:
 Crowbar
 Scissors
Classes of Levers
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2nd class:
 Nutcracker
 Wheelbarrow
 Doors
Classes of Levers
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3rd class:
 Tennis racket
 Tweezers
Questions about Simple Machines
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What is a simple machine?
What are the 6 simple
machines?
How does each simple
machine work?
How does each machine make
work easier?
What are the classes of levers
and how do they work?
What is mechanical
advantage?