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1007 Chapter 9.2 3
Physical
Science 9 Simple Machines
There are six basic types of machines of
which all other machines are composed.
Levers
Pulleys
Wheel & Axle
Inclined Plane
Wedge
Screw
1007 Chapter 9.2 4
Physical
Science 9 Simple Maachines
Levers
All levers have a rigid arm that turns around
a point called the fulcrum.
Force is transferred from one part of the
arm to the other.
The original force can be multiplied or re-
directed to help you do work.
1007 Chapter 9.2 6
Physical
Science 9 Simple Machines
Force can be multiplied
using a lever. This factor
is called the
MECHANICAL
ADVANTAGE
To calculate the mechanical advantage of the
lever, you need to know two things…
1007 Chapter 9.2 7
Physical
Science 9 Levers …the length of the two “arms” of the lever.
The “resistance arm” is the
length of the lever from the
fulcrum to the end of the load.
1007 Chapter 9.2 8
Physical
Science 9 Levers …the length of the two “arms” of the lever.
The “effort arm” is the
length of the lever from the
fulcrum to the end of the effort.
1007 Chapter 9.2 11
Physical
Science 9 Levers Mechanical Advantage
6m
Effort arm
Resistance arm
2m
This means that any
force on the effort arm
will be multiplied by 3.
1007 Chapter 9.2 12
Physical
Science 9 Levers
6m
2m
As with all machines,
the amount of work
that is done is
constant (remember
W=Fd).
With this lever,
your force is
multiplied by 3,
but your
distance is only
1/3 of the effort
distance.
1007 Chapter 9.2 13
Physical
Science 9 Levers
You may push the
lever down 3m, but
the weight will only be
lifted 1m.
3m down
Only 1m up
1007 Chapter 9.2 14
Physical
Science 9 Levers
You may push the
lever down 3m, but
the weight will only be
lifted 1m.
3m down
Force of 3N
W=Fd=3N*3m=9Nm
Only 1m up
Fd=9N*1m=9Nm
1007 Chapter 9.2 15
Physical
Science 9 Levers Mechanical Advantage
6m
Effort arm
Resistance arm
2m
If the weight of the block
is 30N, how much force
would you need
to lift it?
30N
?
1007 Chapter 9.2 16
Physical
Science 9 Levers Mechanical Advantage
Effort arm Resistance arm
30N 10N
1007 Chapter 9.2 17
Physical
Science 9 Levers Mechanical Advantage
A man could lift the Earth with
a long enough lever (and
assuming he had a place to
put the fulcrum and assuming
gravity was constant).
The Earth has a mass of about 6 x 1024 kg. If
the man had a mass of 50kg, and if the
resistance arm was 1m in length…
1007 Chapter 9.2 18
Physical
Science 9 Levers Mechanical Advantage
A man could lift the Earth with
a long enough lever (and
assuming he had a place to
put the fulcrum and assuming
gravity was constant).
…then the effort arm would have to be 1.2 x
1023 km, or 13 million light years (the center of
our galaxy is about 100,00 light years).
1007 Chapter 9.2 19
Physical
Science 9 Levers Mechanical Advantage
A man could lift the Earth with
a long enough lever (and
assuming he had a place to
put the fulcrum and assuming
gravity was constant.
At that distance, if you were to push down on
the lever at 1m/sec, it would take a million
million years to raise the Earth 1cm.
1007 Chapter 9.2 20
Physical
Science 9 Levers Mechanical Advantage
A man could lift the Earth with
a long enough lever (and
assuming he had a place to
put the fulcrum and assuming
gravity was constant.
Levers can multiply your force, but there is a
distance penalty. The higher the MA, the less
the object will move.
1007 Chapter 9.2 21
Physical
Science 9 Levers Mechanical Advantage
Effort arm Resistance arm
What is the mechanical advantage of this
lever?
22m 6.2m
1007 Chapter 9.2 22
Physical
Science 9 Levers Mechanical Advantage
Effort arm Resistance arm
What is the mechanical advanage of this
lever?
22m 6.2m
3.5
1007 Chapter 9.2 23
Physical
Science 9 Levers Mechanical Advantage
Effort arm Resistance arm
22m 6.2m
3.5
If the man has
a mass of
61kg, how
much mass
can he lift with
this lever?
210kg
1007 Chapter 9.2 24
Physical
Science 9 Levers Mechanical Advantage
3.5
If the man
lowers the
lever by 3m,
how far will
the load be
raised up?
210kg
.9m
1007 Chapter 9.2 25
Physical
Science 9 Levers Mechanical Advantage
3.5
The Force is
multiplied by
3.5, but the
distance is
divided by 3.5.
210kg
.9m
1007 Chapter 9.2 26
Physical
Science 9 Levers Mechanical Advantage
3.5
Remember,
simple
machines do
not reduce the
amount of
work that is
done!
210kg
.9m
1007 Chapter 9.2 27
Physical
Science 9 Levers Mechanical Advantage
How much
would you
have to weigh
to lift this
3,400N
elephant? Effort arm = 42m
Resistance Arm = 3.0m
First, calculate the
MA of this lever…
1007 Chapter 9.2 28
Physical
Science 9 Levers Mechanical Advantage
How much
would you
have to weigh
to lift this
3,400N
elephant? Effort arm = 42m
Resistance Arm = 3.0m
First, calculate the
MA of this lever…
MA=14
1007 Chapter 9.2 29
Physical
Science 9 Levers Mechanical Advantage
How much
would you
have to weigh
to lift this
3,400N
elephant?
Resistance Arm = 3.0m
Since your force is
multiplied by 14,
divide the weight of
the elephant by 14.
You must weigh…
240N
(or 54 lbs).
1007 Chapter 9.2 34
Physical
Science 9 Levers Levers can also be used in reverse to
increase the distance per time…As in a
catapult.
1007 Chapter 9.2 35
Physical
Science 9 Levers Levers can also be used in reverse to
increase the distance per time…As in a
catapult.
Why do you think they
call it a “cat”apult?
1007 Chapter 9.2 39
Physical
Science 9 Levers
2nd Class Levers
Fulcrum (pivot
point) is at the
end of the lever.
Load is in the
middle.
1007 Chapter 9.2 42
Physical
Science 9 Levers
3rd Class Levers
Fulcrum (pivot
point) is at the
end of the lever.
Applied force is
in the middle
1007 Chapter 9.2 43
Physical
Science 9 Levers
3rd Class Levers
Third class levers generally multiply distance
instead of force.
1007 Chapter 9.2 44
Physical
Science 9 Pulleys
Pulleys are modified
levers. The “fulcrum”
is the middle of the
pulley.
The rest of the pulley
behaves like the
“rigid arm” of a lever.
1007 Chapter 9.2 45
Physical
Science 9 Pulleys
A simple pulley
merely re-directs the
force.
It’s mechanical
advantage is 1.
(100N in, 100N out)
1007 Chapter 9.2 46
Physical
Science 9 Pulleys
A multiple pulley
system can have
a mechanical
advantage of
more than 1.
This system has a
MA of 4 (four
pulleys).
1007 Chapter 9.2 47
Physical
Science 9 Pulleys
Multiple pulley
systems are
called “block
and tackle”
pulley systems.
1007 Chapter 9.2 48
Physical
Science 9 Pulleys
As with all simple
machines, pulleys
can multiply the
force, however
the amount of
work that is done
remains the
same.
1007 Chapter 9.2 49
Physical
Science 9 Pulleys
In this system
(used in cranes),
the distance the
weight is lifted is
split between the
4 lengths of wire.
So for every 4
meters of
movement here,
the weight is only
lifted 1 meter.
1007 Chapter 9.2 50
Physical
Science 9 Pulleys
1 Fixed
Pulley
MA = 1
2 Pulleys
MA = 2
3 Pulleys
MA = 3
4 Pulleys
MA = 4
1007 Chapter 9.2 54
Physical
Science 9 Wheel & Axle
A Wheel & Axle is a pulley and/or a
lever connected to a shaft.
Lever Pulley (wheel)
Connecting
Shaft
1007 Chapter 9.2 55
Physical
Science 9 Inclined Plane
Inclined planes are like ramps and
other sloped routes.
1007 Chapter 9.2 56
Physical
Science 9 Inclined Plane
As with every simple
machine, the amount of
work that is done is the
same – it takes less
force to go up this
road, but you have to
travel a longer distance
to get where you are
going.
1007 Chapter 9.2 57
Physical
Science 9 Inclined Plane
The Mechanical
Advantage of an
inclined plane is…
Height
LengthMA
1007 Chapter 9.2 58
Physical
Science 9 Inclined Plane
If you have a road that
is 25km in length, and
goes up 5km, the
mechanical advantage
of the road is 5.
Height
LengthMA
1007 Chapter 9.2 59
Physical
Science 9 Inclined Plane
This ramp
multiplies
your force,
but you’ll
have to push
it farther to
get to the top!
1007 Chapter 9.2 60
Physical
Science 9 Inclined Plane
How many
simple
machines are
in this
picture?
Inclined Plane
Wheel & Axle
1st Class Lever 3rd Class Levers (at least 6)
1007 Chapter 9.2 63
Physical
Science 9 Wedge
A wedge concentrates a force into a small
area, making it useful for cutting things.
1007 Chapter 9.2 64
Physical
Science 9 Wedge
A wedge concentrates a force into a small
area, making it useful for cutting things.
1007 Chapter 9.2 65
Physical
Science 9 Wedge
A wedge concentrates a force into a small
area, making it useful for cutting things.
1007 Chapter 9.2 70
Physical
Science 9 Simple Machines
Review: The six simple machines are…
Levers
Pulleys
Wheel & Axle
Inclined Plane
Wedge
Screw
1007 Chapter 9.2 71
Physical
Science 9 Simple Machines
It’s time to play…
I’ll display the device, you tell
me what simple machine it
is…
1007 Chapter 9.2 80
Physical
Science 9 Compound Machines
A compound machine is a machine that
uses two or more simple machines.
2 levers, each with a
wedge (for cutting), and a
screw (which acts as a
fulcrum for the levers).
1007 Chapter 9.2 81
Physical
Science 9 Compound Machines
A compound machine is a machine that
uses two or more simple machines.
A bicycle has numerous
simple machines.