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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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