First How Things Work Encyclopedia

First How Things Work

Encyclopedia

REVISED EDITION Contents
Project editor Olivia Stanford

Editor Radhika Haswani
Senior designer Nidhi Mehra
US Senior editor Shannon Beatty
US Editor Lindsay Walter-Greaney
DTP designer Dheeraj Singh
Picture researcher Sumedha Chopra
Jacket co-ordinator Isobel Walsh
Jacket designer Kartik Gera
Managing editors Laura Gilbert, Alka Thakur Hazarika
Managing art editors Diane Peyton Jones, Romi Chakraborty

Producer Inderjit Bhullar
Pre-production producer Sophie Chatellier

Delhi team head Malavika Talukder
Creative director Helen Senior
Publishing director Sarah Larter

Consultant Jack Challoner

ORIGINAL EDITION Technology
Senior editors Carrie Love, Penny Smith
4–5 Inventions
Senior designer Rachael Grady 6–7 Better by design
Design team Lauren Rosier, Pamela Shiels, 8–9 Early inventions
Karen Hood, Hedi Gutt, Mary Sandberg, Sadie Thomas, 10–11 Modern technology
Claire Patane, Laura Roberts-Jensen, and Poppy Joslin 12–13 Technology all around us
Editorial team Lorrie Mack, Elinor Greenwood, Alexander Cox,
Fleur Star, Caroline Bingham, Wendy Horobin, and Ben Morgan Hard at work

Consultant Roger Bridgman 14–15 Simple machines
Publishing manager Bridget Giles 16–17 Using levers
18–19 On the work site
Art director Rachael Foster 20–21 Moving stuff

This American Edition, 2019 Getting around
First American Edition, 2010
Published in the United States by DK Publishing 22–23 Getting around
1450 Broadway, Suite 801, New York, NY 10018 24–25 Wheels and axles
26–27 Pedal power
Copyright © 2010, 2019 Dorling Kindersley Limited 28–29 Holding the road
DK, a Division of Penguin Random House LLC 30–31 Crank it up
19 20 21 22 23 10 9 8 7 6 5 4 3 2 1 32–33 Engines of fire
001–280455–July/2019 34–35 Race cars
36–37 Up to speed
All rights reserved. 38–39 Powering up
Without limiting the rights under the copyright reserved above, 40–41 Trains and tracks
no part of this publication may be reproduced, stored in or introduced
into a retrieval system, or transmitted, in any form, or by any means
(electronic, mechanical, photocopying, recording, or otherwise), without

the prior written permission of the copyright owner.
Published in Great Britain by Dorling Kindersley Limited.

A catalog record for this book
is available from the Library of Congress.

ISBN 978-1-4654-4349-6

DK books are available at special discounts when purchased in bulk
for sales promotions, premiums, fund-raising, or educational use.

For details, contact: DK Publishing Special Markets,
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Printed and bound in China

A WORLD OF IDEAS:
SEE ALL THERE IS TO KNOW

2 www.dk.com

There is a question at the bottom of each page...

Gases and liquids 106–107 Radio and TV
108–109 Bar codes
42–43 Gases and liquids 110–111 The Internet
44–45 How fluids work 112–113 Search engines
46–47 Float that boat 114–115 Robots
48–49 Floating balloons
50–51 Roller coaster Cutting-edge technology
52–53 How do planes fly?
54–55 Blast off! 116–119 The future
120–121 Anytime soon?
What is energy?
Reference section
56–57 What is energy?
58–59 It’s electric! 122–123 True or false?
60–61 The power of magnets 124–125 Quiz
62–63 Power plants 126–127 What am I?
64–65 Fossil fuels 128–129 Where in the world?
66–67 Renewable energy 130–133 Glossary
68–69 What’s cooking? 134–135 Index
70–71 Keeping cool 136 Acknowledgments
72–73 Energy efficiency
About this book
Light and sound The pages of this book have special features that
will show you how to get your hands on as much
74–75 Light and sound information as possible! Look out for these:
76–77 Now you see it...
78–79 Light and bubbles Gases and liquids Gas molecule Scientists call Gases and liquids The Picture detective
80–81 Mirror, rorriM water molecules quiz will get you searching
82–83 Lenses Gliqausiedssand Gas H2O (H stands Picture detective through each section for
84–85 How light works Air is a gas. The molecules for hydrogen Look through the Gases the answers.
86–87 Fireworks Air and water are in a gas have a lot of energy and O stands and liquids pages and Turn and learn buttons
88–89 Measuring sound important examples of and are always moving and for oxygen). see if you can identify tell you which pages to
90–91 How ears hear two types of substance— colliding. This movement means the picture clues below. turn to in order to find more
92–93 Electric guitar gases and liquids. They they will fill up any container you information on each subject.
behave in different ways. put them in. If there is no container, Liquid Every page is
Digital world they will spread out as far as possible. Liquids always take on the color-coded to show
What’s a molecule? Because there is a lot of empty you which section it is in.
94–95 Chips and codes Liquids and gases are made space between gas molecules, shape of their container. The
96–97 Inside a computer of molecules. Molecules are so gases can be squashed into
98–99 Binary code tiny you can’t see them with the molecules in a liquid are closer
100–101 Sharing data naked eye. Molecules are made of small spaces.
102–103 Cell phones even tinier particles called atoms. together than in a gas, and have less
104–105 Digital photography Everything in the universe is
made of atoms. energy to move around. Special

forces hold the liquid molecules

together. It is very difficult to

squash a liquid into a

Water molecule smaller space.

Air molecules Water molecules Turn
Air is made up of lots of different Water molecules are and learn
Feel the breeze Carbon dioxide atoms bonded together in units Hydrogen made of two hydrogen How ships float:
You can feel air molecules Oxygen atoms bonded to one pp. 46–47
moving when the wind blows. Oxygen Oxygen called molecules. The main oxygen atom. Water
Wind is simply air molecules Carbon molecules in air are nitrogen, molecules are so How
being pushed by a force we sticky, they clump airplanes fly:
call pressure. oxygen, and carbon dioxide. together to form drops.
pp. 52–53
Oxygen Nitrogen

42 43
What do we call materials in which the atoms do not move around?
... check here for the answer.
Digital world Radio and TV A neon lamp sent First TV Radio and TV
Liquid-crystal display.Who inventedlight into holes inThe scientific research for televisions
radio? a spinning disk. began in the late 1800s. John Logie TV inventor
Solids—the atoms in a solid only vibrate in a fixed position.Guglielmo Marconi isBaird’s televisor was the first workingIn 1928, Baird
credited with building It’s hard to imagine life without TV. A rotating disk transformed light demonstrated the first
the first radio system. radio or TV. We use them for TV transmission across
In 1901, he transmitted information and entertainment. from a scene into lines forming a the Atlantic, and the
radio signals across There are millions of programs, moving image. first television program
the Atlantic Ocean. but how do they get to our for the BBC in the UK.
radios and TVs?
How do radios work? Baird’s Transmission today
First called a wireless, the radio televisor Television stations
doesn’t need wires to connect the transmit programs
transmitter and receiver. What’s inside? Images on the The light coming through the through electrical waves. weird or what?
The main parts of a televisor were spinning disk lit up a scene and
Speech and music are turned radio are an antenna, created a moving image. The red Television pictures are These buttons
into electrical signals by a a circuit board with a grainy. The light from the neon lamp made created by cameras, give extra weird
microphone in a radio studio. tuner and amplifier, mechanical the image appear red. mostly in studios. and wonderful
and a loudspeaker. system was soon Programs are sent
The electrical signals from the replaced with a out from the studio over facts.
speech and music travel through Digital radio better quality wires as electrical waves
wires to a radio transmitter. electronic system. or microwaves.
Waves can be sent up to
The radio transmitter sends When you listen to a digital radio, there is little LCD TV satellites in space and
out radio waves from the LCD (liquid crystal display) screens are used in TVs, then sent back to Earth.
radio station. or no interference, for example, from hissing calculators, and watches. LCD screens, and more
recent OLED (organic light-emitting diode) screens, Satellite dishes can
Traditional radio sets pick up noises. Digital transmitters send out sound codes are made up of millions of tiny squares called pixels. pick up the microwaves
the radio waves and turn them and send them to TVs
back into speech and music. that are all mixed up together. The interference along a cable.
A TV turns the waves
Digital transmission can’t affect the codes much, and your radio will into the pictures and
Digital radios also use a transmitter, sound that make up
but the waves they use are different Antenna usually be able to understand them. a TV program.
to those from a traditional radio.
The antenna is If you look weirdTheorerarwe hat?
usually at the very closely roughly 1.6 billion
back of the radio. at an LCD TV television sets in the world!
It picks up the screen, you That’s one TV for every
radio waves. can see
the pixels. four people on
Digital radios use codes Inside the radio the planet.
made of lots of ones is a tuner and Color
and zeros. They are a computer chip squares 107
transmitted over a large that decodes Pixels contain
band of radio waves. the waves and blue, red, and
converts them green color. The
What does LCD stand for? into sound. combination of
different colors in
the pixels form the
images we see.

106

3

Technology Accidental ideas

Inventions Inventions can
happen by accident.
Any new idea or product that When chemist John
has been created by a person Wesley Hyatt was
can be called an invention. trying to find a
Inventions change the way material for billiard
people live their lives—they balls, he spilled a
can make things safer, easier, liquid that dried into
faster, or cheaper. a tough, flexible film.
This “celluloid”
was later used as
camera film.

Knowing your stuff

Technology is the science of how things work. The
inventors of the shoes shown in this drawing knew
that a coiled spring is a source of stored energy.
They used this technology to make power shoes.

Expensive origins
Some of the things

in everyday use were

developed for space

programs. Smoke

detectors, for example,

were first used on the

“Discovery consists of seeing what Skylab space station.

everybody has seen and...

Telephone Electric lightbulb

Refractometer Faraday’s Cathode
Wheel induction ring ray tube

Eyeglasses

4

When was the first pair of shoes invented?

I can find a use for that! Inventors Inventions

Some inventions end up very Inventors are creative Leonardo da Vinci sketched a design
different from what was planned. people. The Italian for a helicopter 500 years before the
Scientist Dr. Spencer Silver invented artist and scientist
a glue that wasn’t sticky enough, Leonardo da Vinci first successful plane flight.
so he thought it was useless. But was an avid inventor.
his coworker Art Fry used it to He designed hundreds
stick bookmarks into his hymnal. of machines, including
The bookmarks wouldn’t fall out, airplanes, pumps,
but they could be moved around. and cannons, that
And so the sticky note was born! were centuries ahead
of their time.

The first military helicopter,
designed by Igor Sikorsky,

took to the skies in the 1940s.

How long does an
invention take?
An invention has to begin with an

idea. It can sometimes take hundreds

of years before the science, technology,

or materials are advanced enough

to make the idea work. The idea for

a helicopter may have come from

China as far back as 400 bce. else has thought.”

... thinking what nobody —Albert Szent-Györgyi

Wimhurst voltage Microscope
generator
Tea maker

Camera

Electric
guitar

People in Mesopotamia made the first leather shoes in 1500 bce. 5

Technology Eddystone Lighthouse, also
known as Smeaton’s Tower
Better
by design New and improved

Anyone can be an inventor. Design engineer John
Many successful inventions Smeaton didn’t invent
came from engineers who used lighthouses, but he did
their knowledge of materials design a new shape for them.
(such as iron) to try new things. The curved tower was wider
at the base than the top, and
could stand up to storms.

oofbnaJaontshheoednashSkhimsatrepdeaeeet.soignn

US inventor Thomas Edison That was my idea!
patented an amazing
1,093 inventions. If someone thinks their idea is
good, they can patent it. Patents
are official documents that
describe the idea and show who
came up with it, so no one else
can steal it and say it’s theirs.

From that...

Since the telephone was invented in
1876, people have changed its design
to make it better. Early telephones
were large and boxy. Making a
call may have involved winding
a handle or turning a dial.

6

Who is often called the “father of the cell phone”?

Better by design

Meet an engineer

Isambard Kingdom Brunel was a 19th-century
British engineer who designed bridges, tunnels,
ships, and even an entire railroad. He worked

a lot with iron and knew it could be used in
ways that had never been tried before.

Brunel’s Royal Albert Will it sell?
Railway Bridge was Inventions can succeed or
built in 1859. It’s the fail depending on whether
only one of its kind. or not people want them.

Making a difference Sneakers were a success!
Can you imagine playing
The way something looks a sport in any other shoes?
can be just as important
as how it works. The first LEGO® was a success!
Apple iMac’s colorful These plastic bricks are one
design made it stand out of the best-selling toys in
among other computers, the world.
so more people bought it. Microwave ovens were a
success! They completely
changed the way many
people cook.
Sinclair C5 was a
failure. Not many people
wanted to buy a battery-
powered tricycle.

... to this!

Today’s cell phones are small by
comparison, and they can do much
more than just make phone calls.
You don’t even need to
use your hands to call a
friend on some of them.

What will
they think
of next?

The American engineer and inventor Martin Cooper. 7

Technology

Early inventions

Some discoveries and inventions seem so
basic it’s hard to imagine life without them.
Yet, someone had to be the first to
create fire, wheels, shoes, and paper.

c. 7000 bce c. 2000 bce

For the first time, people Spoked wheels were
knew how to start a fire. lighter and more useful
Later, they would learn to use than solid ones. Two-
fire in metalwork to create tools. wheeled chariots could
move very fast.
c. 3500 bce c. 2500 bce
The first wheel was
made from solid wood. Early welding involved
hammering heated metal
Experts think it was parts together until they
invented in Mesopotamia fused. As a result, all kinds of
metal objects could be made.
(modern-day Iraq).

7000 bce 2250 bce

c. 6500 bce c. 3000 bce c. 1700 bce

Before mirrors were Reed pens and brushes Evidence of early plumbing (drains and pipes)
made, people would see were used by the ancient can be found among the ruins of the Palace
their reflections in pools Egyptians for drawing symbols of Knossos, on the island of Crete.
of still water. The first on papyrus (which was used
mirrors were created before the invention of paper).
from highly polished
obsidian, a type c. 6000 bce c. 4000 bce
of volcanic stone.
The ancient Egyptians Wooden plows were pulled
used bundles of by animals to cut and turn
papyrus reeds to soil for farming.
make reed boats.
They used the boats
for trade.

8

What does the “c.” in “c. 6000” mean?

Early inventions

c. 1000 bce c. 500 bce c. 300 bce

The earliest underfloor heating system The Greek abacus was a table The Chinese
was found in modern-day Alaska. with counters that people used discovered that a free-
to make calculations. Today’s moving magnet will
The Romans invented their own system familiar abacus with rods and point north—and so
in Europe about 500 years later. beads was invented in China the compass was born.
almost 2,000 years later.
c. 1000 bce c. 50 bce
The first magnets
were simply lumps of Paper was invented
magnetite, a naturally in China more than
occurring magnetic 2,000 years ago, but
mineral. Most the invention was kept
modern magnets a secret for 700 years.
are synthetic.

1200 bce 100 bce

c. 1500 bce c. 640 bce c. 200 bce c. 20 bce
The Archimedes
Most early peoples wore The earliest coins were screw is named Although glass-making had
sandals, but in Mesopotamia used in ancient Greece, after the Greek been around for more than
scientist Archimedes, 2,000 years, the invention
people crafted leather India, and China. of glass-blowing in Syria
shoes to protect Before this, goods who explained that
their feet. would be exchanged water can travel made it possible to create
upward along a glass items in many shapes.
for other items. turning screw.

c. 1200 bce

The first ships were built by
Phoenicians and Greeks to carry
large amounts of cargo for trade.

It stands for “circa,” which means “approximately.” 9

Technology

Modern technology

Today, the phrase “modern technology” is usually used to
mean computers. But a few hundred years ago, steam power
and mechanical presses were new and exciting technology.

1436 1565 1826

The first books Historians think The first photographic image was
were copied by the first pencil was taken by Joseph Niépce in France. He
hand. Gutenberg’s invented by Conrad had to leave his camera still for 8 hours!
movable type and Gesner in Germany.
printing press 1608
made it possible
for books to be Dutchman
produced more Hans Lipperhay
quickly. invented the
telescope—
although some
people think
his children
made one
while playing!

1400 1500 1600 1700 1800

Important ideas

An invention can lead to
so many others that it
changes the world.

The first machines and
factories used to mass-
1700s produce goods led to the 1829
Industrial Revolution.
1764 Stephenson’s Rocket
1800s For the first time, people pulled the first successful
could safely harness the James Hargreaves’ steam train. It reached
power of electricity. spinning jenny
made thread for cloth a top speed of about
faster than ever before. 28 mph (45 kph).

The microprocessor 1769
made computers
1970s smaller and started James Watt’s improved
the Information Age. steam engine was used to
power all kinds of machines.

10

Why was the printing press so important?

1903 Modern technology

The first powered 1977
flight took place
in the US. The The first personal computers
plane, the were large, chunky machines
Wright Flyer, that had very little memory
was made of compared to today’s models.
wood and cloth.

1876 1878 1957

Alexander Graham Bell The lightbulb was The Soviet Union’s
got the first patent for invented around the same Sputnik 1 was the first
a telephone, although time in two different man-made space satellite.
others nearly beat countries—by Thomas
him to it. Edison in the US and
Joseph Swan in Britain.

1926 2012

The televisor was the first kind 3-D printers have made
of television. It was replaced by it possible to manufacture
electronic television in the 1930s. solid objects from
digital information.

1900 2000

1885 WWW

Karl Benz made the first 1990
gas-powered car in
The invention of the World Wide Web
Germany. By 1896, there meant that anyone could get information
were 130 Benz cars from across the world over the Internet.
on the roads.

1895 1979 1998

German scientist Wilhelm This year saw The first handheld
Röntgen (accidentally) the first public e-book reader could
discovered the X-ray. cell-phone store 10 books or
system, in Japan. 4,000 pages.
1938
2010
Laszlo and Georg Biró’s
ballpoint pen had fast- The iPad®, a type
drying ink and didn’t need of touchscreen, mobile
to be refilled very often. computer with a built-in
battery, is one of the
most popular tablets.

iPad® mini 11

More books were made, so knowledge and ideas could spread more easily.

Technology Which tecaround us favorite?
hnology is your
Technology all Turn
and learn
The use of science to create new Space travel:
and better machines and ways of pp. 54–55
doing things is called technology. Robots:
Every day you use technology in pp. 114–115
one of its many different forms.
Here are a few of them.

Chemical Mechanical
technology is
used to make Mechanical technology is the design,
plastics and production, and use of machines, such
refine crude oil. as wind-up clocks and other appliances
that do not use electrical, electronic,
12 or computer technology.

Chemical

Using the science of chemistry to turn raw
materials into more useful things, such as
plastics, cosmetics, or medicine, is called
chemical technology.

Electrical

Technology that deals with electrical
circuits and equipment is known as electrical
technology. It is commonly used in the design
and construction of electronic gadgets, such as
cell phones and televisions, and power grids.

How does nanotechnology get its name?

Technology all around us

Digital

In digital technology, information is
recorded using combinations of 0 and
1 to represent words and pictures. This

system allows huge amounts of data
to be squeezed into tiny spaces.

Biotechnology

This term refers to technology that is
based on biology—the study of living
things. Biotechnology is commonly used in
agriculture and food production. Genetic
engineering is one kind of biotechnology.

Medical

Anything (such as a tool, machine,
process, or substance) that is used to
diagnose, observe, treat, cure, or prevent
people’s illnesses or injuries comes under

the heading of medical technology.

Information When you log on to
a computer, you use
The study, design, and use of information technology.
electronic information systems is
known as information technology. Sunscreen Antibacterial
The term covers machines such as silver bandage
NANO
computers (hardware) and the SUN Odor-
programs they run (software). resistant socks
SPF
Nanotechnology

Modern science can create materials
and simple machines much too small for

you to see under a normal microscope.
This nanotechnology is used in products

such as special sunscreens and textiles.

From the Greek word “nano,” which originally meant “dwarf.” 13

Hard at work Class 1 lever

Simple In class 1 levers, the fulcrum is in
machines the middle. The force you apply
at one end can be magnified at
the other end.

It’s hard to hit a nail into wood with Solid part Magnified
your hand, but much easier with a force
hammer. Tools, such as this one, are
called simple machines. They help Fixed point Load
people work faster and better. Fulcrum
Force you
A small movement from your hand apply
travels down the handle to the head.
As the head moves, it stores energy. Class 2 lever

When the head hits the nail, the In class 2 levers, the fulcrum is at
stored energy is released as a one end and your hands apply a
large force that can split wood. force at the other end. This creates
a magnified force in the middle.

Force you Magnified force
apply

Load

Fulcrum

Feel the force Class 3 lever

Tools, levers, and pulleys are all simple machines. A class 3 lever reduces the force
They increase the size of the force you apply, so you applied between the load and
can perform a job with less effort. When you use a fulcrum. They are used in tweezers
hammer, you need to move the handle only a small and other tools that pick up small,
amount to give the head enough energy to push the delicate objects.
nail through wood.
Reduced
Levers move loads force

Levers are simple machines with a solid part that Force you
turns around a fixed point, called the fulcrum. They apply

help magnify or reduce a force. There are three Fulcrum Load
different types of lever: class 1, class 2, and class 3.

14

What is a force?

Fulcrum Pulley power Simple machines

Pulleys are used to lift heavy Picture detective
loads. A pulley is a length of rope
wrapped around one or more Look through the Hard
wheels. Adding wheels to the at work pages and see
pulley system creates more lifting if you can identify the
force—but you have to pull the picture clues below.
rope farther to lift the load.

A pair of scissors is made of two class 1 Wheel
levers. You apply force with your fingers,
and this force is magnified at the blades,
giving them the power they need to cut
through paper or other materials.

Pulling on the The weight
end of the rope of the load
is distributed
will shorten between the
the rope that’s two lengths
wrapped around
the pulley and of rope.
lift the weight.

Fulcrum Rope
A wheelbarrow is a class 2 lever. It
magnifies the weak force from your
arms to pick up the heavy load.

Fulcrum Load Load
The fulcrum in this pair of chopsticks Pulley with Pulley with
is at the point where the girl holds single wheel multiple wheels
them. Her fingers apply the force
that opens and closes the chopsticks Turn and
to pick up food. learn

Cranes:
pp. 18–19
Conveyors:
pp. 20–21

The power that makes things move or stop. Simply, a push or a pull. 15

Hard at work Levers at home
These are all compound
Using levers levers—tools made up
of more than one lever.
Every time you open a door, ride a
bike, or even bend your arm, you are Nutcrackers are a pair
using levers. Many of the objects we of class 2 levers that are
use every day depend on leverage to joined at the fulcrum.
magnify forces and make tasks easier.
Tweezers are made up
Magnifying forces of two class 3 levers. They
reduce the force you apply.
The amount by which a lever magnifies a force
depends on how far the force you apply and the Pliers comprise of two class
force the lever produces are from the fulcrum. 1 levers. They magnify the
force applied on the handles.

Force you apply Force you apply Force you apply
Force from lever Force from lever
Force from lever

Fulcrum Fulcrum Fulcrum
If the force you apply is the same distance If the force you apply is twice as far from If the force you apply is three times as
from the fulcrum as the force the lever the fulcrum as the force the lever produces, far from the fulcrum as the force the lever
produces, the two forces are equal. the lever doubles the force. produces, the lever triples the force.

Crowbar Force you apply

One of the simplest kinds Force from lever
of lever is the crowbar, which
is a class 1 lever.You use a Force
crowbar to pry very heavy from lever
objects off the ground. The
longer the crowbar is, the Load
more the force is magnified at
the other end. However, you Fulcrum
have to move the long end Moving the crowbar a long way
of the crowbar much farther provides enough force to lift the
than the short end will move. heavy rock a short distance.

16

What class of lever do bottle openers and tongs fall under?

Using levers

Human body Force you
apply
Your arms and legs can act
as levers. When you stand
on tiptoes, your lower leg
works like a class 2 lever.
The powerful calf muscle
pulls up your heel, lifting your
body weight (the load), while
your toes form the fulcrum.

Load

Force you Fishing rod Fulcrum
apply The rod also works as a class 3 lever
When you use a fishing rod to when you haul in a fish.
Load cast a line, the rod works like a
Fulcrum class 3 lever.Your hand applies
a powerful force near the base

of the rod to create a smaller
force at the tip of the rod.

Although the force is weaker,
the tip moves much farther
and faster than your hands,
magnifying the speed.

Seesaw

A seesaw is a class 1 lever.You use the force
of your body weight to move the seesaw. If two
people of equal weight sit at equal distance from
the fulcrum, their weight will balance. But if one
of them sits farther from the fulcrum, their weight
is magnified and the seesaw tips over.

A small child could balance the
weight of an elephant by sitting
far enough away from the fulcrum.

Force you apply

Fulcrum

Bottle openers are class 2 levers. Tongs are class 3 compound levers. 17

Hard at work The long arm
of the crane is
On the called the jib.
work site
The crane’s
Digging dirt, lifting loads— operator sits
there’s lots of heavy work to inside a A wheeled cart
do on a construction site, and small cab.
lots of large machinery to do
it.Yet most of these machines runs along tracks
use fairly simple science to in the jib to move
do their jobs. the load outward.

A slew ring
allows the top of
the crane to turn
around in a circle.

Tower

Why don’t cranes fall over? Hydraulic ram

Tower cranes pick up and move the
massive blocks of concrete and steel
used to construct large buildings. A
huge concrete “counterweight” on the
rear arm of the crane balances the load
carried by the main arm (jib). This
stops the crane from toppling over.

Large weights must be lifted close to
the main tower, while small weights
can be picked up at the end of the jib.

Jib

20 tons
Counterweight

Tower 20 tons 10 tons 7 tons

Each of these loads is balanced, but the
crane could not pick up all three at once.

18

What is a crane’s first job when it arrives at a construction site?

On the work site

Pulleys in action

Cranes lift objects with a hook and
pulley. A steel cable is looped around
pulley wheels on the hook and
jib, and wound in by a motor
in the crane’s rear arm.
Each loop of cable
magnifies the crane’s
lifting force.

Diggers Hydraulic cranes

Diggers use a set of connected levers to Mobile cranes, such as those on fire engines,
scoop earth out of the ground. The levers are hydraulic cranes. Like diggers, they use
are joined like the parts of a human arm,
the bucket forming the “hand.” They are hydraulic rams to apply the force needed
to lift loads. By varying the size of the metal
moved by hydraulic rams— tubes in the rams, the hydraulic system can
metal tubes that extend as produce huge lifting forces—enough to raise
oil is pumped into them.
bridges, trains, and even entire buildings.

Like pulleys and Boom
levers, hydraulic rams Slew ring
can magnify forces.

When the bucket
is pushed inward,
its sharp teeth dig
into the ground to

scoop out dirt.

The slew ring at the
base of the arm
allows the arm to
rotate (turn around).
Bucket

It builds itself, adding one section at a time to its tower. 19

Hard at work A gravity conveyor
seen from above
Moving stuff

From airports and factories to stores and offices,
conveyors are used in all kinds of places to make
it easier to move loads from one point to another.

Move along

The simplest type of conveyor is a gravity conveyor. It
is made up of lots of rollers or wheels in a frame. As each
roller or wheel turns, the load gets shifted to the next.

Luggage and other cargo are moved on The drive pulley, connected to The motor is hidden
conveyors behind the scenes at an airport. an electric motor, does the work. away under the bed
to take up less room.
Up, down, and sideways The motor turns very fast—
1,750 times a minute! A
Belt conveyors can move loads up, speed reducer is added
down, and sideways. The load sits so the drive pulley will
on a belt that turns around rollers, not turn so quickly.
called pulleys. The drive pulley is
connected to a motor, which
makes it rotate.

20 Chain Sprocket

When was the first escalator used?

Going up! Moving stuff

It’s not just boxes that are How to drive
moved around on conveyors—
people are too. Escalators are The parts that make a
moving staircases, with each conveyor belt turn are
separate step connected to called the conveyor drive.
a conveyor belt. Sprockets and chains are
part of this. The chain sits
An escalator can carry more The handrail is in the gaps between the
than 10,000 people in an hour. also turned by the sprocket’s teeth so it doesn’t
motor so you can slip. When the motor
hold on safely. sprocket turns, the chain
moves and turns the drive
The steps are connected to pulley sprocket.
two belts. Wheels near the
top of each step follow the Sprocket
drive belt, which is turned

by the motor.

Drive pulley The steps flatten out at
Electric the top and bottom of
motor the escalator so you don’t
trip getting on and off.
Sprocket
Inner rail

Drive belt

The belt loops all the way Guide wheels
around the bed and pulleys. at the bottom
of each step roll
Bed along the inner
rail to keep the
To stop the belt steps stable. Tail pulley
from sagging,
it is sometimes tucked The tail pulley 21
around small rollers is turned by
called return idlers.
the moving belt.

The first working model was made in the US in 1895 and used as a fairground ride!

Getting around Energy

Getting around = Energy sources

We can all use our legs for getting To move or do any kind of
around, but they’re a bit slow and work you need energy. We get
won’t take us far without making us energy from our food; vehicles
tired. What we need is something that use fuel or electricity.
can get us from one place to another
fast—a vehicle of some sort.

But what does Energy-rich oil
it take to get
a car racing One of the best sources
of energy is oil. When
along a road? oil is burned, it releases
lots of energy.

Turn Types of fuel
and learn Vehicles can get their
energy from many
How bicycles different types of fuel.
work: pp. 26–27
Gas is made from
Car engines: crude oil. Most cars
pp. 32–33 run on gas burned
in the engine.

Diesel is also made
from crude oil. It
D produces more
energy than gas.

Electricity can be
used to power some
cars but is mainly
used by trains.

Solar energy
comes from the sun.
It can be stored for
use by cars.

22

What moves faster than anything else in the universe?

Force Movement Getting around

Getting going On the move Picture detective
Look through the Getting
Once you have enough With its engine turned around pages and see if
energy, you can use it to off, friction will slow you can identify the picture
create forces that will help a vehicle to a stop. clues below.
you move. Forces are To keep it moving,
simply pushes or pulls. the engine must keep
turning the wheels.

PUSH

Speeding up
Increasing the speed at

which an engine turns

the wheels will make the

PULL vehicle go faster. This
is usually done by

increasing the flow

of fuel to the engine.

Wheels turn by Brakes work
using opposing by pushing
forces. As the tire pads or discs
pushes back against against the
the road, the road wheels.
pushes the wheel
Slowing down
forward.
Brakes have pads made
Friction of high-friction materials;
pressing the pads against
Friction is a force that stops the wheels slows the vehicle
things from moving by down to a stop.
pulling them in the other
direction. Without its gripping
action, you wouldn’t be able
to walk or drive anywhere.

Light. 23

Getting around Wheels and axles

An axle is a simple rod that connects two
wheels. For nearly 6,000 years, the wheel
and axle have made it easy to move objects.

Friction Fixed axle Wheel

Friction is the force created A fixed axle can be found on simple
when two surfaces touch. carts. The axle is attached to the cart
As you slide an object, you and the wheels turn independently,
create a lot of friction. When allowing the cart to move.
you roll it on wheels, you
create less.

Pushing this box is The axle
hard work. The large does not
area of the box in turn.
contact with the floor
creates sliding friction. Some friction is
created as the wheel
A lot of friction turns against the axle.
Carts have big wheels so
Put the box on wheels they don’t get stuck on
and it gets easier. bumpy roads. The large
The wheels turn and wheel provides extra grip.
change sliding friction
into the less forceful,
rolling friction.

Less friction

Wheels of history The first use Bicycles,
of wheels which allow
Historians believe the very first and an axle us to create
wheels were used 7,000 years was on our own
ago by potters to make pots. horse-drawn power, have
Later, the wheel was used to chariots been popular
help move and transport objects. around for nearly
3500 bce. 200 years.

24

What is the largest wheel in the world?

Spoke support Outer rim Spoke Wheels and axles
Hub
The little rods that connect the outer rim Other wheels
Wheels don’t just move
to the inner hub of the wheel are called you or your belongings.
They have a diverse
spokes. They make the wheel lighter, range of uses.

yet strong enough to take the weight. A steering wheel is the
fifth wheel on a car and
They also spread the weight evenly helps guide it.

and transfer power from the axle. Gears use interlocking
“teeth” to transfer
The wheels turn Gears Rolling axle movement and power.
with the axle.
Modern cars and vehicles Pulleys and levers use
Axle use a rolling axle system. wheels to help move
The axle is connected to heavy objects.
the engine and helps turn
the wheels. Waterwheels create
mechanical energy when a
The engine turns a rod known river’s current turns them.
as the driveshaft. This uses
Driveshaft gears to transfer the engine’s
power into the axle.

The turning weirTdhe or` what?
force created by
tweel is a
the axle moves
the wheel.

brand-new car wheel that
doesn’t need a tire. Instead, it
uses flexible spokes, which bend
with the bumps on the road.
The tweel will never get
a flat like a tire.

With the In “two-wheel drive” cars, one axle The modern-
invention of powers just two wheels. “Four-wheel day wheel is
the engine, drive” cars are powered by both a high-tech
bigger vehicles axles, moving all four wheels. device. Racing
needed bigger cars use special
wheels to help After a few wheels for
move heavy early designs, different racing
cargo. the motor car conditions.
was built and
its wheels 25
were covered
with air-filled,
rubber tires.

The High Roller, a Ferris wheel in Las Vegas, stands 550 ft (167.6 m) tall.

Getting around Pedal power

The history of bikes A bicycle is a lean, mean
travel machine. Bikes are
The dandy horse (1817) was the so efficient they can
first type of bike and had no pedals turn 90 percent of
at all. Riders had to push forward the energy you put
with their feet until they came to into pedaling into
a downhill slope. forward motion.

The velocipede (1863) had pedals Get in gear
that were fixed to its wheels and had
no gears. This meant the wheel turned Bike gears are cogs (wheels
once for every turn of the pedal. It took with teeth) that are linked by
huge effort to travel fast. a chain. Using different gears
High Wheelers (1872) got around makes pedaling easier or faster.
the problem of fixed pedals by having Bikes can have up to 30 gears.
a huge front wheel. They were faster
but also dangerous—it was a long When a small gear
fall down from the saddle. at the front wheel is
connected to a large
gear at the back, the
bike is in low gear.
This turns the wheel
slowly but forcefully,
so is ideal for
traveling uphill.

The safety bicycle (around 1884) When a large gear at the front wheel is
was the original name for a bicycle connected to a small gear at the back, the bike
with gears. It had the same basic is in high gear. The wheel will turn several times
design as those used today. for each rotation of the pedals. This is ideal for
speeding along on flat land or racing downhill.

26

The main picture shows a BMX bike. What does BMX stand for?

Handlebars are used to Brakes work when you squeeze Pedal power
control the front wheel. Moving the brake lever on the handlebars.
the handlebars lets you change It pulls a cable that’s connected to Bike types
direction and also helps you brake shoes on either side of the front
keep your balance as you cycle wheel. The rubber shoes grip onto the Utility bikes are used for everyday
along. Handlebars are levers, wheel like a clamp. This creates friction cycling. A chain guard stops the oily
and the longer they are, the against the wheel, slowing it down. chain from getting your clothes dirty,
easier they are to turn. and bags can sit safely in the basket.
Frames of most modern
bikes are the “diamond”
kind—a shape made
up of two triangles of
hollow steel, which is
light but strong.

Mountain bikes have
a strong frame and
wide tires for extra
grip on rough ground.

Pedals turn the up-and-down Track-racing bikes are designed for
motion of your legs into the speed. The rider must bend low to hold
circular movement of the wheels. the handlebars, making a streamlined
shape. They have no brakes!
Tires have patterns weird or what?
called treads that Recumbent bikes have frames that
increase friction between The world’s longest make the rider lean back in their seat.
the bike wheel and the true bicycle (one with Some have covers, too. They can be
road surface, so the bike just two wheels) was tricky to ride, but can go very fast.
is easy to control and built in the Netherlands
keeps a good grip, even in 2002. It was 92 ft 27
in rainy conditions.
Wheels have spokes (28 m) long!
that carry the weight
of the bike and the rider.

Bicycle Motocross, a cycling sport in which BMX bicycles are used for racing and stunt riding.

Getting around Holding
the road

Why do trucks and tractors
need such big wheels? It’s
to help them get a grip on
slippery surfaces and move
easily while pulling loads.

Losing your grip Sticking to the surface

This car’s wheels can’t get Heavy vehicles need big tires to help spread
enough grip to move on a the weight of the trucks and their loads.
muddy road. Mud is wet, The tires move the vehicle using friction.
slimy, and does not have any As the tires press down and backward on
snags or bumps to provide the road, the road pushes the vehicle forward.
friction. Also, the car’s small
and smooth wheels do not Tractors overcome this
provide enough surface area to problem by having
reduce the pressure of the car’s wide tires with
heavy weight on the deep treads
ground.You’re stuck! that provide
a better grip.

Tractor

The sloping ridges
push mud out from
Car under the tire.

28

How big is the world’s largest tire?

Holding the road

Monster trucks

What do you get if you put
the body of a pickup truck on a
bus axle? A monster truck! Add
some tractor wheels and a good

suspension system, and you
can bounce over anything.

Smoothing out the bumps Inside the shock absorber is a
piston that pushes against
When you hit a bump in the road, a gas. The gas slows the
your wheels move up and down. piston down and turns
This is because of the vehicle’s its energy into heat.
suspension system. It is designed
to absorb the impact through Spring Cross Shock absorber
the tires, springs, and section
shock absorbers.

Tire

Tires Springs Shock absorbers
Tires are left slightly soft so they can There is a spring around each shock These are pumps filled with gas
squash over small bumps without absorber that reduces the impact that absorb the energy of the
moving up and down. by squeezing and stretching. wheel hitting the ground.

29
It is 80 ft (24 m) tall and weighs 12 tons (11 metric tons).

Getting around Crank it up

Many forms of transportation use
wheels, which push against the ground

and use friction to move. But what
makes the wheels turn?

Up and down, around and around

To ride a bike, you move your legs up and down
on the pedals. The pedals turn cranks around and
around, which turn the wheels. A car’s wheels
move in a similar way.

Cylinder

Gear Pistons

Crank Crankshaft

Pedal Cranks
A car has pistons instead of
Rear-wheel drive pedals to move the cranks.

A bike’s cranks turn a chain that
is connected to the back wheel, so
when you pedal, you are actually
powering only one wheel. Many bikes
have gears to make pedaling easier.

Types of engine A lawnmower has This motorcycle has two
only one cylinder. This large cylinders. Their slow
Different vehicles means only one piston up-and-down motion gives
have different goes up and down to the Harley its distinctive
numbers of cylinders. turn the wheels. thumping sound.
Generally, the larger
the vehicle, the more
they have.

30 Lawnmower Harley Davidson

How many parts are there in an average car?

Crank it up

Secret cylinders This car, like the bike,
is driven forward by
There is a row of metal cylinders hidden its back wheels.
deep in a car’s engine. The pistons
inside them pump up and down, 4 The driveshaft turns
just like your feet on a bike. the wheel axles
Start at stage 1 in the and the wheel
diagram to see how axles turn the wheels.
the pistons power
a car’s wheels.

Car pistons are also Axle
attached to levers Axle
called cranks. These
2 turn the crankshaft.

The pistons pump up Piston Driveshaft 3
and down like legs. Gearbox
The crankshaft
1 turns the driveshaft
through the gearbox.

Crankshaft Turn
and learn
Rotation relay
Internal
The pistons are connected to the combustion engine:
crankshaft, which, in turn, is connected to the
driveshaft. The driveshaft is connected to the pp. 32–33
axles, and the wheels go around and around. Race cars:
pp. 34–35

A Formula 1 racing car needs an This huge cargo ship is five
extremely fast and powerful stories tall. It weighs over
engine. It has 8 cylinders. 2,500 tons (2,300 metric tons)
Formula 1 car and has 14 cylinders, each
one bigger than a person.

Emma Maersk

Around 30,000. 31

Getting around

Engines of fire

Most cars and other vehicles burn What makes it burn?
fuel to release the energy needed
to move. This happens inside an Fuels such as gasoline and diesel burn
internal combustion engine—an easily. All they need are a spark and
engine that is powered by lots oxygen, which is a gas found in the air.
of little fires.

Recipe for fire: Exploding with power

Fuel + Oxygen + A spark = Fire At normal speed, a car’s engine
lights around 50 little fires every
second. The fires make pistons
shoot up and down, with four
“strokes” for every fire—suck,
squeeze, bang, and blow.

1 Air is sucked in Spark plug 2
through this valve. Air and
Squeeze
Suck Fuel enters fuel
the valve mixture The valve that
through a lets in the air at the
fuel injector. top closes, trapping
everything inside.
The piston moves The piston moves
up, squeezing the
down, sucking in air air and fuel mixture
tightly together.
through a valve. A
The crankshaft
tiny squirt of fuel is continues to turn,
pushing the piston up.
injected into the air

at the same time.

One turn of the
crankshaft makes the

piston move down.

32

What actually is fire?

The pistons are found Fuel burns inside Engines of fire
deep in the engine, the cylinders.
fitting snugly into These valves let air
The cylinders hollow cylinders. and fuel in and
burnt gases out.
The combustion (burning)
happens in an engine’s Cylinder
cylinders. The energy Piston
released by each tiny
explosion is directed to
the pistons, causing them
to move up and down. This
drives the crankshaft around
and around, which turns the
wheels (see pp. 30–31).

Crankshaft

3 The spark plug 4
releases a
Bang Blow
spark into the
mix—BANG! Finally, the piston
moves back up
When the piston and pushes the Waste gases blow
burned gases out out of this valve,
reaches the top, a of the outlet valve. on the way to the
These gases leave exhaust pipe.
carefully timed spark the car through
the exhaust.
sets fire to the gas.

The gas burns very

quickly, forcing the

piston back down.

It’s a high-speed chemical reaction that produces heat and light. 33

Getting around

Race cars

Formula 1 cars are like normal cars in Pit stop pressure
many ways. They have gas engines,
gears, and steering wheels. However, At pit stops, a driver refuels and
they are built with only one thing in gets new tires. This is all done in
mind, and that’s WINNING RACES! about 30 seconds. That’s about
the same amount of time as it
A technical masterpiece takes to read this paragraph!

Every bit of a Formula 1 (F1) car is light and very The car’s spoilers create a downward
strong. At its peak speed of 225 mph (360 kph), force that stops the car from flying
air flows over it with the force of a tornado, away while traveling at high speeds.
so it is built to be as low and streamlined
as possible. Even the driver’s helmet
is part of the streamlining.

The blue arrows show
how air flows over
the car as it races.

34

What is the minimum weight of Formula 1 race car?

Race cars

G-force The car accelerates

While driving at super-high speeds, Water spills out backward.
a Formula 1 driver experiences a pushing
force called g-force, which can be up to six The car brakes
times more powerful than gravity. It can
shove a driver backward, forward, and Water spills out forward.
sideways as the car twists around the track.
You can see g-force at work in a normal The car turns right
car by watching water sloshing in a cup.

This helmet is attached to
the seat to stop the driver’s
head from swinging around
because of g-force.

Inertia Water spills out to the left.

G-force is caused by inertia. The law of inertia The car turns left
says that moving objects try to travel straight
at a constant speed. When a car stops abruptly, Water spills out to the right.
your body tries to keep going forward.

Steering wheel

Because an F1 driver is
concentrating so hard
on winning a race and
because the inside of
the car is so tight, all
the controls for the car
are close to the driver’s
hand on the steering
wheel. There are
only two foot pedals—
the brake and the
accelerator.

Buttons like these fulfil all an F1 driver
needs, from traction control to drinks
dispenser—drinks are pumped by tube
straight into the driver’s mouth.

35
Including the driver and excluding fuel, the minimum weight is 1,630 lb (740 kg).

Getting around Up to speed

70 80 90 100111020 Once you’re on the move, you usually
60 want to go as fast as you can. But what
makes sports cars really fast and tankers
50 130 really slow? Speed isn’t just about
40 raw power—other factors are at work.
30 mph 140
150
20 10

Speed, velocity, Acceleration isn’t just speeding
and acceleration up. Scientists also use it to
describe all changes in velocity,
You measure speed by dividing like slowing down and even
the distance traveled by the changing direction.
time it takes. Speed is not
the same as velocity, which
is a measure of how fast
you are going in a
particular direction.You
feel acceleration when
you pedal your bike
really hard. Acceleration
measures how quickly
your velocity is changing.

Horsepower?

Engine power is still measured using a very old unit—the horsepower. It is
based on how many horses would be needed to provide the same amount
of pulling power. The average car engine has around 135 horsepower.

36

How fast are electric cars?

Up to speed

Pulling power

If you have a powerful engine,
you can accelerate very fast,
which is why a sports car will
always beat a lawnmower. But
if you give a lift to an elephant,
your acceleration will suffer.
That is because it takes more
force to speed up heavy objects.

Milk tanker vs. Ariel Atom

Both have a 300 horsepower engine.
A full tanker can weigh as much
as 100 tons (110 metric tons).
The Atom weighs half a ton

(0.55 metric tons). Even though they
have the same pulling power, the

weight of the milk means the tanker
takes 35 seconds to accelerate from

0 to 60 mph (0 to 97 kph). The
Atom can do it in 2.7 seconds,

making it one of the fastest
accelerating road cars in the world.

Not such a drag

No vehicle ever made can accelerate as fast as a drag racing car, or dragster.
They can go from 0 to 330 mph (0 to 531 kph) in less than 4.5 seconds.
Dragsters use nitromethane as fuel, which provides twice as
much power as gas. The rear wheels have to be really
big to transfer the high power made by the engine.

Superfast cars
If you want to go really fast and break records, then there’s only one solution—strap a
jet engine or two to your chassis. Jet engines don’t use pistons. Instead, they suck air
through the front of the engine, use it to burn fuel, and then blast the hot exhaust out
of the back. This pushes the car forward at speeds of up to 760 mph (1,223 kph).

The Tesla Roadster can reach a speed of 130 mph (209 kph). 37

Getting around

Powering up

Most cars are powered by gasoline Electric car
engines, but there are many other
ways to power a vehicle. Today, Electric cars use rechargeable
renewable forms of energy that don’t batteries instead of gas.
depend on fossil fuels such as gas The batteries release energy
are being used more widely. in the form of electricity, which
drives a motor that runs the
Solar cars work best Solar car car. While it is easy to charge
in very sunny places. such cars, it can take hours.
They tend to be flat, The solar panels on a solar
and very wide or car use sunlight to generate A solar panel is
long to create room electricity. The electricity powers made of lots of
for the large solar an electric motor that turns separate units
panels on the roof. the wheels. Solar cars are not called cells.
powerful, and so are usually
very light and streamlined.

The curved front and flat body
make the car streamlined, which
reduces the energy it needs to
run smoothly.

38

When did the hybrid car go on sale?

Biofuel Corn is mixed with water Powering up
and left to ferment.
Many ordinary cars can Hydrogen power
run on biofuels—fuels made The sugar in it turns to alcohol,
from plants. Biodiesel, for which is added to gas. Hydrogen-powered vehicles use
instance, is a biofuel made liquid hydrogen as a fuel. The
from vegetable oil. In some
countries, including Brazil hydrogen flows into a device called a
and the US, gas is diluted fuel cell, which combines hydrogen
with alcohol made from corn with oxygen from the air to make
or sugarcane. Using biofuels water and electricity. The electricity
reduces pollution, but this can drives the car’s motor and wheels,
harm the environment—vast just as in an electric car. The
areas of land are used up to water is released as exhaust.
produce these fuels.
In some hybrids, the gas engine
Fuel tank drives the wheels, but in others it
merely charges the batteries.
Battery
Gas engine

Hybrid car

Hybrid cars Electric motor

Hybrid cars are powered by Air car
a combination of gas and
electricity from batteries. In The air car works a bit
some hybrid cars, when the like a balloon. High-pressure
car stops, the brakes capture air is stored in an air tank.
the energy released and use When the driver pushes the
it to charge the batteries. A accelerator pedal, the air is
computer switches between released through a valve. This
the two forms of power to jet of air turns the engine.
make the best use of energy.
39
In 1917.

Getting around

Trains and tracks

Most countries have a railroad system This train’s cars tilt to
where trains travel on steel tracks. Trains help it travel around
are often powered by electricity that
runs through rails or overhead wires. corners at high speed.

Engine and Diesel electric
generator unit
Some electric trains
run on diesel fuel. Most freight trains
The diesel is burned are fueled by diesel.
to make electricity.
This electricity
powers the motors
that make the
wheels turn and
the train move.

Electric third rail Train wheel

Several trains use an electrified third
rail. The train picks up the electricity
using a device called a shoe.

Shoe
Electrified

rails are
dangerous.
You can be
killed if you step
on the third rail!

Overhead wires

There are trains that draw electricity from
overhead wires using a metal arm. The cables
carry high-voltage electricity—around 25,000 volts.

The train’s metal arm
is called a pantograph.

40

What is a maglev train?

You need wheels Signals Trains and tracks

Trains have metal wheels with Signals tell the train Train travel
a rim, called a flange, on the engineer when it is safe to Trains can transport a
inside to stop them from move forward, when to large number of people
slipping off the track. Usually proceed to the next section and goods efficiently
the flanges never touch the of track, and when to stop. across long distances.
rails, but if they do, you hear Signals use red-, yellow-,
a squealing noise. and green-colored lights, Freight trains carry
just like traffic lights. goods and can be
more than 2 miles
Wheels are (3.5 km) long.
slightly cone shaped.
Bullet trains in
Flanges Japan are the world’s
first high-speed
Rails rail service.

A tie is a block that Wheel The French TGV is
supports the rails and centrally the fastest train ever
placed on rail. built. It can go at
holds them in place. 357 mph (575 kph).
Straight track Eurostar travels
between England and
On the tracks France through the
Channel Tunnel, which
Railroad tracks guide trains from station to station. They runs under water.
are made of steel and usually welded together to give a The Trans-Siberian
smooth ride. Some rails are moveable. These are called Express makes the
points. They help the train switch from one track to another. longest journey—
5,857 miles (9,297 km).

The Qinghai–Tibet
railroad is the world’s
highest—passengers
need to carry oxygen.

A B
C
Points

Points The rail is Braking on ice
The rail sits in joined to ties,
metal “seats” which keep the Metal wheels can slip when
that are bolted two rails the right the engineer brakes on icy rails.
onto the ties. distance apart. So a small amount of sand is
The track is laid dropped in front of them to
on ballast made help them grip the rail.
from broken stone.
41
A train that uses electromagnetism to lift it off the ground and move forward.

Gases and liquids Gas molecule

Gliqausiedssand Gas

Air and water are Air is a gas. The molecules
important examples of in a gas have a lot of energy
two types of substance— and are always moving and
gases and liquids. They colliding. This movement means
behave in different ways. they will fill up any container you
put them in. If there is no container,
What’s a molecule? they will spread out as far as possible.
Because there is a lot of empty
Liquids and gases are made space between gas molecules,
of molecules. Molecules are so gases can be squashed into
tiny you can’t see them with the
naked eye. Molecules are made of small spaces.
even tinier particles called atoms.
Everything in the universe is
made of atoms.

Air molecules
Air is made up of lots of different
Feel the breeze Carbon dioxide atoms bonded together in units

You can feel air molecules Oxygen Oxygen called molecules. The main
moving when the wind blows. Carbon molecules in air are nitrogen,
Wind is simply air molecules
being pushed by a force we oxygen, and carbon dioxide.
call pressure.
Oxygen Nitrogen

42

What do we call materials in which the atoms do not move around?

Scientists call Gases and liquids
water molecules
fHo2rOhy(dHrosgtaennds Picture detective
and O stands Look through the Gases
for oxygen). and liquids pages and
see if you can identify
the picture clues below.

Liquid
Liquids always take on the

shape of their container. The

molecules in a liquid are closer

together than in a gas, and have less

energy to move around. Special

forces hold the liquid molecules

together. It is very difficult to

squash a liquid into a

Water molecule smaller space.

Hydrogen Water molecules Turn
Oxygen and learn
Water molecules are
made of two hydrogen How ships float:
atoms bonded to one pp. 46–47
oxygen atom. Water How
molecules are so
sticky, they clump airplanes fly:
together to form drops. pp. 52–53

Solids—the atoms in a solid only vibrate in a fixed position. 43

Gases and liquids

How fluids work

Gases, such as air, and liquids, such Streamlined car
as water, are known as “fluids.” This
is because they move in a similar A car is designed to be as
way and can flow around corners streamlined as possible, so
and fill containers. air can pass smoothly over it.

Fluid motion Smooth sides mean a fluid has to travel Smooth shape
only a short distance around an object.
Fluids flow smoothly over This produces little or no drag.
curved (streamlined) objects.
They do not flow smoothly Fluid flow
over shapes that have
corners and bumps. These
slow fluids down, causing
a force called drag.

Block shapes with flat edges split the
fluid’s flow into different streams. Some
pass over an object. Some pass around
it. Others twist and turn back, creating
areas of drag known as eddies.

Fluid flow Block
shape

Eddy

Sir Isaac Newton Gravity and weight
discovered gravity
when an apple Gravity is the force that keeps you stuck
fell from a tree. to the ground. It also keeps the moon
in orbit around the Earth, and keeps
the Earth traveling around the sun.
Gravity is what gives you weight.
Without your weight pulling you
downward, you would simply f loat
away as if you were in space.

44

What is denser—water or air?

How dense? How fluids work

The weight of an object depends A pound of bricks weighs
upon its mass—the amount of the same as a pound of
matter it’s made of. Matter is made oranges, but the oranges
of atoms. Substances in which the take up more space. The
atoms are heavy and closely packed mass of the bricks is
are said to be more “dense” than packed into a smaller
substances whose atoms are lighter, space, so we say the
and less closely packed. bricks have a higher
density than the oranges.

Floating and sinking

An object that is free to move in a fluid will either float or sink, depending
on its density and the density of the fluid.

An object will float in air if it is less An object will float in water if it
dense than air. is less dense than water.

The gas inside the balloon is less dense Boats float because they are mainly filled
than the air around it, so it slowly rises. with air, which is less dense than water.

An object will sink in air if it is more An object will sink in water if it is more
dense than air. dense than water.

Apples are denser than air so they drop Brick molecules are very close together,
from trees. making bricks dense, and so they sink.

45
Water has 1,000 times the density of air.

Gases and liquids Floating beach ball

Float that boat

How do ships float, and why Buoyancy Sinking golf ball
do they sometimes sink? It’s
all to do with buoyancy. When an object
weighs less than the
Setting sail amount of water it
displaces, it floats,
A ship is very heavy, especially when or is “buoyant.” If it
it’s loaded with crew, passengers, and weighs more, it sinks.
cargo. But the ship still floats because
as it pushes down, it displaces water,
and the displaced water pushes upward.
If the ship weighs less than the displaced
water, it will float (see p. 45).

The weight of the ship is
spread out across the hull.

Balancing act Gravity
While buoyancy pushes the Buoyancy
boat upward, gravity pulls it
downward. These two forces
balance each other out, so a
ship can float on the water.

46

Which is the largest ship in the world?

Bulkheads are walls that Safety systems Float that boat
divide large areas into
smaller ones in a ship. A ship may sink if it takes on Going down
water. To help prevent this,
Bulkheads ships have safety features Submarines are
such as bulkheads. If one not like other
compartment starts to leak, boats—they
the bulkheads stop the water have to be able
flooding the whole ship. to sink or float
on command.
Double hull They do this
by filling and
A big ship usually emptying their ballast
has a double hull, tanks with air or water.
which is like a tire
with an inner tube. It 1 The weight of Periscope
gives extra protection a submarine’s Valve
if the ship collides hull helps it Compressed
with rocks or icebergs. to go underwater, but it air tank
can’t sink when there is
air in the ballast tanks.
Hull Double hull Most of the air is let out

through a valve. Some air Interior
is compressed (squashed)
into a small holding tank.
Water is then pumped
into the tanks and the
sub sinks.
Ballast Water is
tank taken in
and the
sub sinks.

The steel hull is full of Air flows
air, which is very light into the
and keeps the ship afloat.
2 ballast tanks.
That sinking feeling When the sub is
underwater, air
The air inside a ship’s is pumped back
hull makes the ship less into the ballast tanks
dense than the water until the density of
around it. If the ship hits the sub matches that
a rock and rips a hole in of the water around
its hull, water pours in it. The sub can stay at
and replaces the air. This one level as it moves
makes the ship denser through the water.
and it sinks.
Water is Air fills the
forced out. tanks and
the sub rises.
3 When it’s time
This ship is taking on water to surface, more
and has started to sink. air is pumped
into the tanks, pushing
out the water. Once it’s
at the surface, air is
sucked in to fill the ballast
tanks and the sub floats.

Water is forced out.

A ship called Pioneering Spirit. It is 1,253 ft (382 m) long and 407 ft (124 m) wide. 47

Gases and liquids An airship can rise to more than
6,500 ft (2,000 m). By comparison,
Floating balloons a passenger jet normally cruises at

Why do some balloons rise up into around 30,000 ft (10,000 m).
the air while others drop to the
floor? To understand this,
you have to look at the
gases inside them.

P arty balloons ar e filled with helium gas.

He

Helium Heavy air

This balloon is filled When a balloon is
with a gas called filled with a gas that
is less dense than air,
helium. Helium is less it floats. When it is
dense than air, so this filled with a gas that
is denser than air, it sinks.
balloon floats.

Helium facts

Helium gas has no smell.
It makes up about seven
percent of natural gas.

At parties, helium CO2 Deep-sea divers
balloons are tied breathe in a mixture
down so they Carbon dioxide of helium and oxygen.
don’t float away! Helium boils at a
When you blow up a balloon with very low temperature—
your breath, the air inside contains -452 ˚F (-233 ˚C) and
more carbon dioxide than the air turns to gas.
Helium, found in stars,
outside. It is also under more is named after the Greek
pressure. As a result, the air inside word for the sun—helios.

the balloon is denser than the Liquid helium is colorless
surrounding air, causing and very cold. It helps
the balloon to sink. launch space rockets.

48

What is the only element to be discovered in space before it was found on the Earth?