Levers
In this presentation you will:
 identify the use of levers in hydraulic applications
ClassAct SRS enabled.
Levers
In this presentation you will see first,
second and third class levers.
You will also see hydraulics
applications where levers are used.
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Levers
Mechanical Levers
Levers are simple
mechanisms used to apply
mechanical advantage.
For example, by using a
stiff branch resting on a log,
early man was able to lift
heavy rocks.
A lever can be a long bar
that rests on a pivot point
(fulcrum). An effort is
applied to move the load.
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Levers
Lever Classification
First Class
There are three classes of levers.
They differ in the placement of the
fulcrum, effort and load along the
lever.
The three types are:
 First class lever
Second Class
 Second class lever
 Third class lever
Third Class
Sometimes these are also
referred to as first order, second
order and third order levers.
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Levers
Question 1
The lever shown is a:
A) first class lever
B) second class lever
C) third class lever
Levers
First Class Lever
First class levers are the most common
type of lever. The fulcrum is between
the effort and the load.
Effort
A mechanical advantage of force is
achieved if the distance between the
effort and fulcrum is longer than that
between the load and fulcrum.
The lever will balance if the load and
effort are equal, and they are also
both the same distance from the
fulcrum. The system is in equilibrium.
Fulcrum
Load
A seesaw is an example of a first class
lever. Other examples are a claw hammer,
crowbar, scissors and weigh scales.
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Levers
Second Class Levers
Large load,
small distance
Small effort,
large distance
The load is between the effort and
the fulcrum. Second class levers
provide mechanical advantage of
force, as the effort is always
further away from the fulcrum than
the load.
This allows a large load to be
lifted a small distance by a smaller
effort moving a larger distance.
A wheelbarrow is an example of a
second class lever. Other examples
include bottle openers, foot pumps
and nut crackers.
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Levers
Question 2
In a second class lever, where should the effort be placed?
A) On the opposite side of the fulcrum to the load
B) On the same side of the fulcrum as the load, but further away from the
fulcrum
C) Between the load and the fulcrum
D) On the opposite side of the fulcrum but very close to it
Levers
Third Class Levers
The effort is applied between the
load and the fulcrum. The effort is
closer to the fulcrum than the load.
Effort
Fulcrum
Load
This means the effort force needs to
be larger than the load, but with the
advantage that the load moves a
greater distance than that moved by
the effort.
An engine hoist is an example of a
third class lever. Other examples are
tweezers and fishing rods.
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Levers
Question 3
Which of the following is an example of a third class lever?
A) Wheel barrow
B) Scissors
C) Fishing rod
D) See-saw
Levers
Hydraulic Systems Using Mechanical Levers
Many construction machines make use of the hydraulic lever principle,
whether they are excavating, lifting, grading, or drilling machines.
First class lever
Third class lever
An excavator uses a hydraulic cylinder to push up the boom, but the
boom is itself a type of lever. A short movement of the cylinder makes
the end of the boom move much further.
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Levers
Question 4
On an excavator, what part of the lever mechanism does the cylinder
represent?
A) Load
B) Effort
C) Fulcrum
D) Lever
Cylinder
Levers
Summary
You should now be aware of:
 Different classes of lever
 Examples of levers in hydraulic
systems
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