Levers

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LeversPulleys
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Parts of a Lever
Effort
Load
Load Arm
Fulcrum
A lever is a simple machine used to reduce the
amount of effort it would take to lift a load or
reduce the amount of effort needed to do
work.There are 3 types of levers Class 1,
Class 2, and Class 3. The effort needed to lift
a load is measured in Newtons.
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Classes of Levers
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Class 1 Levers
F
A Class 1 Lever has its fulcrum between the
effort and the load.
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Class 2 Levers
L
A Class 2 Lever has its load between the effort
and the fulcrum.
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Class 3 Levers
E
A Class 3 Lever has the effort between the load
and the fulcrum.
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Levers QuizUse the following slides to quiz
yourself on how how well you can match commonly
used items with their correct class of lever.
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Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class3
9
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class3
10
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
11
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
12
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
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Class 1 Class 2
Class 3
14
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
15
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
16
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
17
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
18
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
19
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
20
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
21
Click on the correct Lever classification for the
tool pictured below.
Class 1 Class 2
Class 3
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Congratulations!
You have successfully matched the common hand
tools with their correct classification of lever.
Be sure to remember F L E
1 2 3
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Levers and Advantage
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Levers can provide Mechanical Advantage by
reducing the effort needed to lift a load. The
closer the fulcrum is to the load, the less
effort is needed to lift the load. The load does
not move a great distance.
L
E
F
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Levers can be used to move loads farther if the
fulcrum is placed close to the effort. In this
situation more effort is needed to lift the load,
but the load will move farther than if the
fulcrum was closer to the load.
L
E
F
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Pulleys
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Single Fixed Pulley
This pulley provides the user Directional
Advantage, allowing someone to pull down to lift
the load up. Is Mechanical Advantageprovided
with this system?
No, the effort needed to lift this load is equal
to the weight of the load. This is because the
load is supported by only 1 rope arm. You must
also pull an amount of rope equal to the height
you wish to lift the load
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Single Moveable Pulley
This pulley system provides Mechanical Advantage,
requiring only ½ the effort needed to lift the
weight of the load. If the load weighs 20 lbs,
only 10 lbs of effort is needed to lift it. Can
you tell why?
The load is supported by 2 rope arms under the
pulley. Each load arm supports half the weight
of the load, so the arm pulling up uses only 10
lbs of effort to lift this load. You must pull
twice as much rope as desired to lift the load a
certain height. Example Pull 2 ft of rope for
each 1 foot of height that you want to lift the
load.
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Single Fixed/Single Moveable Pulley
This pulley system combines the properties of
their single components into a system that
provides both Mechanical and Directional
Advantage.Do you see how this happens? How much
rope must you pull?
This pulley provides Directional Advantage by
allowing the user to pull down to lift the load.
It also provides Mechanical Advantage by using 2
rope arms to support the load, reducing the
effort needed to lift the load by ½.In this
system you pull 2 times as much rope for every
unit of height that you want to lift the load.
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Pulley Power!
Single-Fixed Pulleys provide or Directional
Advantage. You can make use of Counter-Weights in
order to reduce your effort needed to lift the
load. However, your effort PLUS the the
counter-weight together must be equal to or be
more than the weight of the load being lifted.
Single-Moveable Pulleys provide Mechanical
Advantage. You must pull 2 times the distance in
rope that you wish to lift the load because the
load is supported by 2 rope arms. You gain a
Mechanical Advantage of 2 because you are using
only ½ as much effort to lift the load.
Combining Single-Fixed and Single-Moveable into
Compound Pulley Systems allows the user to gain
both Mechanical and Directional Advantage. The
more rope arms supporting the load the greater
the Mechanical Advantage.
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Inclined Planes, Screws, and Wedges
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An Inclined Plane is a simple machine that helps
reduce the effort needed to move a load. Instead
of picking up this load and lifting it straight
upwards, the load can be pushed along an
elevated plane. The user must move the load a
greater distance, but the effort needed to move
it will be less.
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Screw
Inclined Plane
Wrapped around post Screw
A Screw is really an Inclined Plane wrapped
around a center post.
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Wedge
edge
Two Inclined Planes meeting together to create a
sharp edge creates a Wedge.
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Wedges can be put to use in a variety of ways.
The tips of screws, nails, and needles are
wedges. Axes, splitting mauls, and picks have
wedge edges. Scissors blades, pruning shears, and
hand-held grass clippers all have wedge shaped
blades. Planers have wedge shaped shapes for
shaving wood particles. You will find many more
examples if you take a closer look at many of the
common tools used around your own house. Wedges
are just one form of Simple Machine that helps us
do work more easily.
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Simple Machines allow users to more easily
accomplish work. This PowerPoint presentation is
a tool that you can use to review these concepts
and prepare for the upcoming FOSS Assessment for
theLevers and Pulleys module.