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SCIENCE 5. UNIT 7. MACHINES & STRUCTURES C.E.I.P. SANTA ANA (Madridejos)
CONTENTS:
1.– MACHINES: simple / complex.
2.– Simple machines:
Wheel, lever, screw, inclined plane, pulley...
3.- Complex machines: parts.
Casing, motor, circuits, mechanical elements...
4.– Tools: hand tools / power tools.
5.– STRUCTURES: types, parts…
6.– Technological advances, scientists and inventors.
A machine is something that helps us to do a work
with less effort.
There are simple machines and complex machines.
USEFUL WORDS:
.– machine .– simple .– complex
.– wheel .– axle .– lever
.– fulcrum .– effort .– load
.– screw .– jack
1.– MACHINES.
A machine is something that helps us to do a work with
less effort. For example a bike helps us to move easier than
walking or running, a calculator helps us to save time
when we must do calculations.
There are two types of machines: simple machines and
complex machines.
1.1.– SIMPLE MACHINES.
A simple machine has only one or a few parts or components. From ancient times humans have used this kind of
machines.
Scissors
Calculator
Washing machine
A.– Wheel & axle:
The invention of the wheel was into the Neolithic period.
A wheel is a circular component that rotates on an axle, and
reduces friction, so makes easier the movement.
The wheel and the axle help us to transport heavy objects
in an easy way.
wheel
axle
Model of an old cart.
B.– Lever:
This machine is formed by a rigid bar, that moves around a fixed support called fulcrum. It is used to transmit a
force, to move heavy objets…
There are three classes of levers, depending if the fulcrum, the load or the effort are in the centre.
Load effort
FULCRUM
fulcrum
effort
fulcrum Load
First-class lever:
Fulcrum in the centre.
Second-class lever:
Load in the centre. Third-class lever:
Effort in the centre.
C.– Screw:
We use a screw to hold things together or lift objects.
Turning a screw is easier than pushing the screw directly.
LOAD
EFFORT
Screw can hold things together.
car
jack
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USEFUL WORDS:
.– inclined plane .– pulley .– wedge
.– complex machine .– casing .– sensor
.– screen .– microchips .– gears
.– rack & pinion .– chain drive
D.– Inclined plane:
An inclined plane or ramp, is a flat supporting surface
with one end higher than the other, used for raising or lo-
wering heavy objects.
It’s easier to push an object up on an inclined plane than to
lift it vertically.
inclined plane
E.– Pulley:
This machine has a wheel, an axle and a rope or chain.
If we pull down the rope, we lift an object fixed to it.
Pulling the rope is easier than lifting the object using our
body.
pulley An old pulley.
F.– Wedge:
This machine has a pointed end and one thicker end
(triangled-shape), that is used to split something or to sepa-
rate two things. We can do it push down with a hammer.
Splitting a trunk with wedges.
1.2.– COMPLEX MACHINES.
A complex machine has a lot of components and simple machines working together. It needs electricity or other
kind of energy to work.
Main parts of a complex machines:
a.– Casing: is the outer part of the machine, and protects it.
b.– Motor: some machines like cars, drills… have motors to
produce movement (electrical or combustion motors).
c.– Electric and electronic circuits, microchips... control
different functions of the machine. They need electricity to
work.
d.– Sensors and screens: Sensors receive information from
the machine and from the exterior. Screens give us informa-
tion about the functioning of the machine.
Load
Effort
Pulley
e.– Mechanical elements:
e.1.– Gears: change direction, speed,
amount of a force…
e.2.– Rack and pinion convert rota-
tional motion into linear motion.
e.3.– Chain drive is used for trans-
mission of mechanical power in ma-
chines (bikes…)
pinion
rack
Casing Sensors & screen
Gears, pinions, chains...
Motor
Simple machines: formed by one or a few components. Wheel and axle / lever / screw / inclined plane / pulley / wedge
Complex machines: has lots of components. Casing / motor / circuits / sensors / screens / gears /
rack and pinion / chain drive
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USEFUL WORDS:
.– tools .– hand tools .– power tool
.– hammer .– screwdriver .– pliers
.– wretch .– drill .– lawnmower
.– food mixer .– structure .– framework
4.– TOOLS:
Primitive humans started to use tools thousands of years
ago. First tools were made of stone, wood or parts of ani-
mals like bones. Later they were made of metals, that were
harder and more useful.
Nowadays there are specific tools for every type of job, and
we can divide them into groups:
A tool is any physical instrument that you use with
your hands to make or repair something easier.
There are hand tools and power tools.
Prehistoric
stone tools.
Carpentry tools from
16th century.
4.1.– Hand tools:
They are tools that you can only use them with your hands.
They don’t need any power or another type of energy.
Some examples of hand tools are hammers, screwdrivers,
scissors, wrench, pliers...
4.1.– Power tools:
They are tools that work with a power source. The most
common have electric motors. They are used in industry,
contruction, garden, housework, drilling, cutting...
Pliers
Hammer
Scissors
Screwdriver
Adjustable Wrench
Hand tools
Power tools
Drill
Cement mixer
Microwave oven
Lawnmower
Food mixer
5.– STRUCTURES: TYPES & PARTS. A structure is a framework formed by intercon-
nected parts, that can resist weights and forces,
and must be stable and strong.
There are structures in everywhere. In nature, living beings
are formed by structures. Structure must hold more than its
own weight and other forces like wind, water... so they must
be strong.
For example, vertebrates are formed by a skeleton. Skeleton
is a structure made up by bones, some invertebrates have an
exoskeleton that holds and protects the rest of the body.
5.1.– Types of structures:
They are two types of structures:
.– Natural structures: Produced in nature by living beings,
like skeletons. In plants, the structure of cells can support the
weight of the plant. Birds built nests for their baby birds…
.– Artificial structures: designed and made by humans.
Examples of them are buildings, bridges...
Storks nest.
Paper wasps nest.
Structure of a house. Structure of Tower Bridge (London).
NATURAL STRUCTURES
ARTIFICIAL STRUCTURES
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5.2.– Parts of a structure:
Most of structures must resist three kind of forces.
If we think of a house...
1.– The weight of the structure itself (metal structure).
2..– Extra weight (walls, windows, furniture, people…)
3.– Other forces (wind, water, earthquakes…)
Most of structures have common parts:
.– Foundations: base of the building (underground).
.– Pillars: vertical parts.
.– Beams and girders: horizontal parts.
.– Archs, staircase, triangular structures...
Foundations
Pillars
Beams
Triangular structures
Structure of a
block of flats. Staircase
1.– TECHNOLOGICAL ADVANCES, SCIENTISTS & INVENTORS.
From prehistoric times, people have improved tools and
machines. We are using more and more machines every-
time for everything.
Nowadays, there are lots of technological advances that
we use instead of old inventions .Normally machines
and inventions are improving because scientists and in-
ventors are working on new technologies everyday.
In ancient times, sailing was very complicated because it
was very easy to get lost in the sea. At the end of the
Middle Ages, the compass was brought from China, so
Christopher Columbus could discover America.
Nowadays we don’t use the compass, instead, we use
GPS (Global Positioning System) in our mobiles, cars,
planes...
From compass to GPS.
Cars at the end of 19th century were very diffent than cars now.
Mercedes Benz (1886)
speed 19 km/h.
.– foundations .– pillars .-beams /girders .– arch .– staircase
.– triangular structure .– GPS (Global Positioning System)
Renault (1889)
speed 50 km/h.
Ford T (1901) Citroën Traction Avant (1934)
Volkswagen beetle (1938) Seat 600 (1957) Jeep Grand Cherokee (2010) Ferrari (prototype)
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