Machines and Movement
By: Ms. Haynes
Content
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What is a Machine?
How do machines
make work easier ?
Classification of
Machines
Simple Machines
Levers
First Class Lever
Second Class Lever
Third Class Lever
Levers in the
Mammalian Skeleton
▪ Pulley Systems
▪ Single Fixed Pulley
▪ Single Movable Pulley
▪ Multiple Pulley/Block
and Tackle Pulley
▪ Inclined Plane
▪ Other Simple Machines
▪ Force Multiplier
▪ Distance Multiplier
 Complex Machines
 The Bicycle
 The Motor Car
 Mechanical
Advantage
 Energy Conversion in
Machines
 Inefficiency of
Machines
 Caring for Machines
What is a Machine ?
▪ Machine is any device which make work easier by
reducing the effort (force need) to over come
another force called the load.
How do Machines make work Easier ?
▪ Redirecting the effort – We usually find it easier to pull downwards
than to lift upwards.
▪ Spreading the energy we use over a longer period of time – It is
easier to use a little energy for 10 seconds than to use a lot of
energy for 1 second. The total amount of energy required is the
same but we don’t have to supply it all at once.
▪ Acting as Force Multipliers – Some machines convert a small force
into a much larger force. They often change the direction of the
force
Classification of Machines
Simple
Machines
Complex
Simple Machines
▪ Lever
▪ Pulley
▪ Wedge
▪ Inclined Plane
▪ Screw
▪ Wheel and Axle
Complex Machines
▪ Two or more simple machines working together.
Lever
▪ A lever consists of a bar or a rod that
can move freely at a fix point called the
pivot or fulcrum.
▪ The effort is the force need to make the
lever move and the load is the object
being moved.
▪ The effort and the load are applied to
either side of the beam.
First Class Lever
First Class Lever
▪ In a first class lever the fulcrum is
located between the load and
effort.
▪ If the fulcrum is closer to the load
less effort is needed to move the
load a shorter distance.
▪ If the fulcrum is closer to
the effort, then more effort is
needed to move the load a longer
distance.
First Class Lever
Scissors
Hammer
Lower Limb
Second Class Lever
Second Class Lever
▪ In a second class lever the load is
located between the effort and the
fulcrum.
▪ If the load is closer to the fulcrum
than the effort then less effort is
required to move the load.
▪ If the load is closer to the effort than
the fulcrum then more effort will be
required to move the load
Second Class Lever
Wheelbarrow
Bottle Opener
Nutcracker
Third Class Lever
Third Class Lever
▪ The effort is located between the
load and the fulcrum.
▪ If the load is closer to the
fulcrum than the effort, then less
effort will be required to move the
load.
▪ If the load is closer to the effort
than the fulcrum, then more
effort will be required to move the
load.
Third Class Lever
Broom
Fishing Rod
Tong
Levers in the Mammalian Skeleton
• This type of lever is
found in the neck
when raising your
head to head a
football.
• The neck muscles
provide the effort, the
neck is the fulcrum,
and the weight of the
head is the load.
Levers in the Mammalian Skeleton
• This type of lever is found in
the ankle area.
• When standing on tiptoe, the
ball of the foot acts as the
fulcrum, the weight of the
body acts as the load and the
effort comes from the
contraction of the
gastrocnemius muscle.
• This second class lever is
used when taking off for a
jump or pushing against the
blocks in a sprint start.
Levers in the Mammalian Skeleton
During a biceps curl, the
fulcrum is the elbow
joint, the effort comes
from the biceps
contracting and the
resistance is the weight
of the forearm and any
weight that it may be
holding.
Pulley Systems
Diagram showing the different [pulley systems – fixed pulley,
Movable Pulley and Block & Tackle.
Single Fixed Pulley
▪ This pulley has one grooved wheel and
is attached (fixed) to an object.
▪ The only advantage of this type of
pulley is that it changes the direction of
the force (Re-direction of the effort).
Single Movable Pulley
▪ The movable pulley is attached to the load and
moves with it.
▪ The effort is reduced by half, therefore it is a force
multiplier. The mechanical advantage is two.
▪ If the load has a weight of 6 Newtons then
the sections of the rope labeled T and E
will together support the weight.
▪ This means that the effort needed to lift the load
will only be 3 N, that is half the weight of the load.
Multiple Pulley/Block and Tackle
▪ This is made up of two or more pulleys.
▪ The upper block is attached (fixed) to a
support and the lower block is free to
move.
▪ The load is attached to the lower block.
▪ In this pulley system the load is
supported by four sections of the rope
and therefore it's weight is equally
distributed among the four sections.
It makes work easier by:
• Redirecting effort
• Spreading the effort over a
longer period of time
Inclined Plane
▪ An inclined plane is a slanted
surface that can be used to raise
or lower things.
▪ An inclined plane does not
move.
An inclined plane makes work
easier by spreading the effort
over a longer period of time.
Inclined Plane
Stairs
Ramp
Slide
Other Simple Machines
Name
Description
Wedge
A wedge is two inclined planes that are back to back. Wedges hold things
together or split them apart. E.g. Nails, Staples, axe, Knives
Screw
A screw is a form of an inclined plane in which the plane is wrapped around
an axis or a pole.
Wheel and Axle
It consists of a wheel attached to a rod like axle. The wheel and Axle can be
used to increase the speed by which a particular task is done, but this
always increases the amount of the effort (force) required to do the task.
Other Simple Machines
Wheel & Axle
Wedge
Screw
Force Multiplier
▪ Force multipliers increase the force but reduce the distance
.They convert a small force into a much larger force. They
often also change the direction of the force.
▪ For Example: A can opener – the force to open the can is
applied by pulling up on one side of the can opener. The
fulcrum turns this into a downward force on the can lid
Distance Multiplier
Distance multiplying machines actually reduce the force that
is transferred to the load from the effort. For example:
▪ The Lever at the Elbow
▪ The Bicycle
The Bicycle
 Wheel and Axle – The
wheels of a bicycle are
wheel and axle.
 Levers – The pedals are
parts of a lever . The gears
shifts and brake controls on
the handle bars are levers
too.
 Pulley – The lever with the
pedals turns a pulley that
holds the bicycle’s chains
The pedals do not move as far as the wheels, so
the distance is being multiplied. One rotation of
the pedals can produce one rotation of the
wheels, which are much bigger.
Motor Car
 Windshield – An inclined plane (flat
surface at an angle that deflects
wind downwards thus helping the
driver to see without wind blinding
him.
 Pedal – Inclined plane because it is
an angle so you don’t have to push
straight down.
 Seatbelt–Pulley, Works by
changing the direction of the force
thus keeping someone in their seat
 Gearshift – Lever, helps to move a
heavy load by applying pressure to
one end.
Mechanical Advantage
▪ The mechanical advantage of a machine is the ratio of the load to
the effort.
▪ The larger the mechanical advantage, the easier the machine
makes doing work.
Mechanical Advantage
▪ This formula used to calculate mechanical advantage is:
▪ NB. Load and effort is measured in a unit called newton (N)
Mechanical Advantage
▪ Calculate the mechanical advantage when an effort of 10N
is applied to one end of a crowbar to move a rock of weight
30N
MA= L/E
MA= 30N÷10N =3
▪ Mechanical advantage has no unit because it is a ratio
Mechanical Advantage
▪ Calculate the mechanical advantage when an effort of 20N
is applied to one end of a crowbar to move a rock of weight
60N
▪ A force of 10N raised a load of 400 kg. Calculate mechanical
advantage of the machine.
▪ A pulley is used to raise a heavy box. The pulley is such that
an input force of 123 N is needed to provide an output force
of 1545 N. What is the mechanical advantage of this pulley?
Energy Conversion in Machines
▪ When we use machines we do work. We can calculate
the work done using the formula:
Work done (Joule) = Force (Newton) ×Distance moved
(meter)
▪ NB. 1 newton meter (Nm) = 1 Joule (J)
Energy Conversion in Machines
For example:
▪ How much work is done pushing a 300N box 3m above the
ground?
Work done = force × Distance
Work done= 300N × 3m
900 Nm or 900J
Energy Conversion in Machines
▪ Calculate work done on object where applied force is 10N
and distance is 10m
▪ How much work is done pushing a 400N log 2m above the
ground?
Inefficiency of Machines
The more energy that is wasted in a machine, the less efficient is the
machine. Some energy always gets wasted as heat, usually because of
friction between moving parts. The energy in the effort force must do
two things:
▪ It must overcome the friction
▪ It must move the load.
Caring for Machines
Good Maintenance of a
machine keep the
efficiency of the machine
as high as possible. You
then have to use less
energy . Examples of
maintaining machines
include:
Maintenance
Reason
Keeping the engine oil in a car at
the correct level
This reduces friction between the
pistons and the walls of the cylinders
in the engine
Re-sharpening scissors periodically This allows the force on the blade of
by removing any corrosion that has the scissors to be transferred to a
formed
narrower line on the paper/cloth
A larger force is transferred.
Maintaining the electrical
components of the electric motor
of a chain saw
Allows the maximum electric current
to be transferred to the moving parts
of the motor to generate maximum
‘effort’ force.