New Science Connection Textbook P.1-P.6 Sample Chapter

• Animals feed on plants or other animals.

Meat comes Rice and
from animals. vegetables come

from plants.

MarshallCoCpayvriegnhditsh Chicken
drumstick

Fish Rice
Vegetables

Do you remember the animal groups that you have learnt?
What are they?

Do these groups of animals Go to WB Activity 1.3
feed on the same things?

Put on Your Thinking Cap

Recall and compare the characteristics of fish, birds, mammals and
reptiles. You may tabulate your answers using the following headings:

Body covering Reproduction Distinctive
method characteristics

Fish
Birds
Mammals
Reptiles

Classifying Organisms 9

There are fish, birds, reptiles, insects and mammals.
However, insects form the largest group of animals.

In what ways do these insects look alike?
Where do they live?
How do they move?
How do they reproduce?
MarshallCoCpayvriegnhditsh Dragonfly

Mosquito

Butterfly Ant
Grasshopper
Fly
Ladybird
Bee

10 Chapter 1

An ant, like all other insects, has a Feelers
Legs
body that is made up of three parts,

one pair of feelers and three pairs

of legs. Body in

Insects can be found in all types of three parts

places, for example, in rubbish bins,

in the garden, on trees and plants.
MarshallCoCpayvriegnhditsh
Some insects have one or two pairs of wings, which help them to fly.
Other insects have no wings at all and they cannot fly. Instead, they
can crawl.

Dragonfly Fly Silverfish

Insects lay eggs. Their young hatch from eggs.

Put on Your Thinking Cap

Is a spider an insect? Why?

Classifying Organisms 11

Key Ideas Animals

can can be
mammals

birds
fish
moveMarshallCoCpayvriegnhditshrespond feed on
freely quickly to
changes

plants other reptiles
animals

insects

1.3 Characteristics of fungi

Let us look at a mushroom. Does the mushroom look more like
a plant or an animal? Which group does it belong to?

Is the mushroom
• fixed in one position?
• slow to respond to changes?
• green in colour?
• able to make its own food?

12 Chapter 1

MarshallCoCpayvriegnhditshLiving things such as mushrooms, toadstools,
mould and yeast have many characteristics that
plants have. However, unlike plants, they cannot
make their own food.
They belong to a group of living things called fungi
(singular: fungus).
What are the characteristics of fungi?
• They are fixed in one position and respond slowly

to changes.
• They cannot make their own food.
• They feed on dead plants and animals. Some fungi

attack living plants and animals.

These mushrooms
grow on dead logs.

These mushrooms grow
on a tree trunk.

Classifying Organisms 13

Have you seen these fungi? Which are
good for us? Which are harmful to us?

Yeast

MarshallCoCpayvriegnhditshPenicillium growingButton
on orange mushrooms

Cup fungi

Toadstool Mould growing on bread

Put on Your Thinking Cap

The enoki mushroom looks a lot like a bean sprout. Why is the enoki
mushroom a fungus and the bean sprout a plant?

Bean sprouts

Enoki
mushrooms

14 Chapter 1

Going Further My favourite dessert
is white fungus soup
My favourite soup
is chicken and with rock sugar.
mushroom soup.

MarshallCoCpayvriegnhditsh
Can all fungi be eaten? Find out the common names of some edible
fungi. Either draw them or collect pictures of them. Make a poster of
your findings.

Key Ideas Fungi

are can feed on examples
cannot make yeast
fixed in one mould
position respond dead and live
slowly to plants and
changes animals

mushrooms

food toadstools

Classifying Organisms 15

1.4 Characteristics of micro organisms

Are there any living things
that we cannot see with the naked
eye that is, without the help of

instruments such as hand lenses
and microscopes?

MarshallCoCpayvriegnhditsh
There are some living things that we may not be able to see
with the naked eye, but they are all around us. They are called
micro-organisms.

WOW! Antonie van Leeuwenhoek

One day during the 1600s, a Dutch
scientist, Antonie van Leeuwenhoek,
looked at a drop of cloudy water
through his microscope. He saw
many tiny living things! We call these
micro-organisms.

16 Chapter 1

What are the characteristics of micro-organisms?

• They are very tiny, living things.
• They cannot be seen with the naked eye. (They can be seen only

under a microscope.)

• They live in the air, water, soil, in or on the bodies of plants and
animals.

Micro-organisms come in various shapes and forms. Examples
include yeast, amoeba and bacteria.
MarshallCoCpayvriegnhditsh
Bacteria Euglena

Micro-organisms seen
under a microscope

Amoeba Desmid

Classifying Organisms 17

Try This!

View pictures of different types of
micro-organisms on websites.

Key Ideas

Micro-organisms

MarshallCoCpayvriegnhditsharecan be seen can be found

through

tiny microscope in water

in air

in soil

in or on the
bodies of

living things

Review Questions

1. What are the characteristics of plants?
2. What are the characteristics of animals?
3. What are the characteristics of fungi?
4. What are the characteristics of micro-organisms?

18 Chapter 1

Experiment Time!

THE RISING DOUGH

Process skills

observing, comparing, inferring, communicating

What you need

MarshallCoCpayvriegnhditsh
flour, plastic container with cover, baker’s yeast, warm water, plastic spoon

Procedure and observations

Let us make some dough and observe how it rises.

Step 1 Step 2 Step 3

Add a little yeast and warm Use the plastic spoon Cover the container.
Leave the dough for
water to some flour. to mix everything well. 15 minutes.

1. Draw the dough to show its size
a) at the start of the experiment,
b) after 15 minutes and
c) after 30 minutes.

2. What is the effect of the yeast on the dough?
3. How is yeast a useful fungus? Why?
4. Is yeast a micro-organism? Why?

Conclusion Go to WB Revision Worksheet 1

What characteristics of
yeast can you infer from
this experiment?

Classifying Organisms 19





1. Classifying Animals

Do you remember your
last trip to the zoo?
What kinds of animals
did you see?

There are so many How can we
different kinds of living organisms in classify animals into
the world. Scientists need to classify different groups?
these organisms so that it is easy to
Chapter 1 - Classifying Animals 1
study them!

Let’s Look at...

• how to classify animals

1.1 Classification of animals

Fish Owl
Lion
Whale

Butterfly Peacocks Snake Lizard
Dolphin Seal Fly

Grasshopper

Penguin Ant

Cockroach Tiger

Rabbits

Look at the animals above. Classify them into groups based on their
similarities and differences. Compare the way you classify these animals
with the way your friends classify them.

2 New Science Connection 4

Scientists classify animals into two main groups, the invertebrates and
vertebrates.

Invertebrates

Invertebrates make up about 95% of all animals in the world.
Invertebrates are animals without backbones. Invertebrates can be
further classified into several subgroups such as echinoderms, poriferans,
cnidaria, molluscs, worms and arthropods.

Sea urchins

Echinoderms are marine animals that live
in the sea. Most echinoderms have arms
or spines which radiate from the central
portion of their body. Starfish and sea
urchins are examples of echinoderms.

Starfish

Poriferans are sponges. They are found in
the water and have a specialised filter feeding
system. The holes on the sponges help to draw
water in. Special cells in the sponge filter out
the food from the water.

Cnidaria are animals which are found solely in
water. They have stinging cells which can shoot
out tiny poisonous ‘darts’. This helps them to
catch their prey. Jellyfish and some corals are
examples of cnidaria.

Snails

Oysters Molluscs have soft internal organs
covered with a hard outer shell. Oysters
and snails are examples of molluscs.

Chapter 1 - Classifying Animals 3

Worms have soft bodies without legs. Worms can be classified as
annelids, bristle worms, nematodes, flatworms and bootlace worms.
They can be found on land, in water and even in animals.

Annelids are worms with segmented bodies.
Leech Common annelids are earthworms and leeches.

Earthworm Fireworm

Bristle worms also have segmented bodies.
However, they have bristles sticking out from
each segment. Bristle worms are normally found
in aquatic environments. A common bristle worm
is the fireworm.

Hookworms Nematodes (roundworms) have round
unsegmented bodies. Hookworms are
an example of a nematode. They can be
found in animals which have taken in food
contaminated with soil and hookworm eggs.
These can cause painful diseases such as
hookworm feet.

Flatworms are worms with flat bodies.
A common flatworm is the tapeworm.
Tapeworms can be found in animals.
They live in the animals’ intestines and
feed off the nutrients found there.

Flatworms

Bootlace worms are worms which are found
on or near the sea floor. They have long and thin
bodies. Some can grow up to 55 metres in length.

Bootlace worms

4 New Science Connection 4

Arthropods have limbs with joints, a body divided into segments and
a hard exoskeleton. They include animals such as crustaceans, arachnids
and insects.

Crustaceans live mainly

in the water. Crabs and

lobsters are examples

of crustaceans. Lobster

Crabs Scorpion

Arachnids have four pairs of
legs. Spiders, scorpions and ticks
are examples of arachnids.

Spiders

Insects have three pairs of legs and three body Grasshopper
segments. They also have one pair of antennae.
Some insects have one or two pairs of wings which Abdomen
help them to fly. The wingless insects can crawl or Thorax
jump from place to place. Bees and ants are Head
examples of insects.

Ladybird Butterfly
Bee Antennae

Ant

Chapter 1 - Classifying Animals 5

Going Further

Spiders are not insects. If you take a closer look, you will see
that they have only two body segments and four pairs of legs.
Spiders are placed in a group known as the Arachnids.

Vertebrates

Vertebrates are animals with backbones. Vertebrates can be further
divided into mammals, reptiles, birds, fish and amphibians.

Mammals
Mammals are warm-blooded animals. Their body temperatures do not
change with the surrounding temperature. They form the fourth largest
group of animals. They are found in all parts of the world.

Giraffe Elephant Lion Panda Whale

Almost all mammals give birth
to their young. Their mothers
produce milk to feed them.
Examples of such
mammals are
humans, cows, cats
and sheep.

Kittens Mother with child Ewe with lambs

6 New Science Connection 4

Going Further

Not all mammals give birth to live young. The duck-billed platypus
and the spiny anteater are the only two mammals which lay eggs.
Their young hatch from the eggs.

Duck-billed platypus Spiny anteater

The bodies of mammals are also covered with hair or fur.
Are humans covered with hair or fur?

Hamsters

Chimpanzee
Chapter 1 - Classifying Animals 7

Reptiles
Reptiles are cold-blooded animals.
Their body temperatures change
with the surrounding temperature.
Their skins are dry and usually
covered by scales.

Crocodile

Snake

Reptiles can be found in Tortoise
different parts of the world.
Some reptiles such as turtles Flippers help turtles
have legs modified into flippers. to swim quickly.
Flippers allow the turtles to
swim through water quickly.

Young snakes hatching
from eggs

All reptiles reproduce by laying
eggs. The young hatch
from the eggs.

8 New Science Connection 4

Put on Your Thinking Cap

Look at the pictures of dinosaurs.
Which group of animals do you
think they belong to?

Birds

Look at the pictures of the different birds.
In what ways do they look alike?

Parrot

Chicken Pigeon

Swan Mynah

Birds form the third largest
group of animals.

Chapter 1 - Classifying Animals 9

All birds have a beak, a pair of wings, a pair of feet and a body covered
with feathers. The feathers protect the body and help the bird to fly.

Wing

Beak
Feet

However, there are some flightless birds which are
too heavy to fly. Examples include the ostrich and emu.
These birds run on their feet instead.

Emu Ostrich

All birds lay eggs.
Their eggs are kept
warm until their
young hatch.

A swan keeping
her eggs warm

10 New Science Connection 4

Poultry are birds which we rear and eat for food. Chickens and ducks are
examples of poultry.

A poultry farm

Fish
Fish form the second largest group of animals. The picture below shows
a typical fish.

Tail Fins

Scales Gill cover

A fish has a body covered with protective scales. Gills under
It has fins and a tail that help it to swim. It has gills that gill cover

help it to breathe. The gill cover protects the delicate gills from injury.

Chapter 1 - Classifying Animals 11

All fish live and swim in water. Some live in
fresh water while others live in salt water.

A clown fish lives
in the ocean.

A carp lives in
fresh water.

Most fish lay eggs. Their young hatch from eggs. However, some fish give
birth to their young. The guppy, swordtail and molly give birth to their young.

Molly Guppies Swordtails

Go to WB Activity 1.1

12 New Science Connection 4

Amphibians

Amphibians are cold-blooded

animals which have evolved

from animals present during the

age of the dinosaurs. They can Frog
live both on land and in water.
Amphibians lay eggs in water. Salamander Toad

The young live in water and breathe through gills. The adults live on land

and breathe through their lungs. Some common amphibians are frogs,

toads and salamanders.

Key Ideas

Animals
can be classified as

vertebrates invertebrates
such as such as

echinoderms poriferans cnidaria molluscs worms arthropods

mammals reptiles birds fish amphibians

crustaceans arachnids insects

Chapter 1 - Classifying Animals 13

Review Questions

1. What is the main difference between a vertebrate and an invertebrate?
2. List some characteristics of insects.
3. List some characteristics of mammals.

Experiment Time!

Can cockroach eggs hatch to give young cockroaches (nymphs) under
all conditions?

Process skills
observing, inferring, analysing, evaluating, investigating
What you need
four small plastic containers, small tweezers, cockroach egg case (can be found
by looking in dark and damp cupboards), cooking oil
Procedure and observations
1. Pry open the cockroach egg case with the tweezers. Carefully remove the

eggs from the egg case.
2. Place two eggs into each plastic container.
3. Pour cooking oil into one of the plastic containers.
4. Place one plastic container in the laboratory freezer. (Do not use a freezer

used to store food.)
5. Place one plastic container in a warm place such as the back of the freezer.
6. Place one plastic container in the classroom.
7. Observe the eggs in plastic containers.
Conclusion
In which containers do young cockroaches hatch from the eggs? Why?

Go to WB Revision Worksheet 1

14 New Science Connection 4





1. Forces and Their Effects

MarshallCoCpayvriegnhditshWho will win?

What forces are
involved in a game

of tug of war?

Forces and Their Effects 1

Let’s Look at...

• how two forces acting on the same
plane act together or against each other

• air pressure
• water pressure
• why an object floats or sinks
• friction

1.1 What is a force?

A force is a push or pull. Many actions such as stretching a rubber band or
kicking a ball involve pulls and pushes. We cannot see a force but we know that
it exists by observing its effects. A force can:
MarshallCoCpayvriegnhditsh
Make a stationary Make a moving Change the shape
object move object speed up of an object

Slow down a Change the direction Stop a
moving object of a moving object moving object
2 Chapter 1

How many effects of forces can you see in the pictures?

The unit for force is Newton, N. For example, we can say
that John exerts a pushing force of 10 N on the wall.

WOW!

Do you know that
the unit Newton is
actually the name of
a scientist? Sir Isaac
Newton is famous
for his discovery of
gravity and many
other laws such as
the three Laws
of Motion.
MarshallCoCpayvriegnhditsh
Key Ideas Force
can be a
push
pull
Forces and Their Effects 3

1.2 Resultant force

MarshallCoCpayvriegnhditsh
Look at the pictures above.

In which situation will each person exert less effort per person if both cars
weigh the same?

Let us convert them into simple diagrams and see the effects. Assume that
100 N of force is required to move the car in each case.

Scenario 1 100 N pushing force

When only one person is
pushing the car, he needs
to exert a force of 100 N
to move the car.

Forces can be represented by vectors. In the picture above, the arrow
pointing to the left is known as a vector. A vector shows the direction and
size of the force.

4 Chapter 1

Scenario 2 50 N pushing force from each person
50 N (left) + 50 N (left) = 100 N resultant force to the left
However, when two
people are pushing
the car, each person
has to exert only 50 N
of pushing force in the
same direction.
These two forces
add up to give
100 N, enough force
to move the car.
MarshallCoCpayvriegnhditsh
The two forces add up to give us a resultant force. Because both forces are
exerted in the same direction and are coplanar (meaning that they are on
the same level), they do not cancel out each other. Instead they can be added
together.

The resultant force is the sum of all forces acting on an object on a plane
(in one line). To obtain the resultant force, individual forces acting in the same
direction are added together while individual forces acting in the opposite
directions are subtracted.

What happens if the same car is being pushed from opposite sides?

Do you think the car will 50 N pushing force from each person
move? The car will not 50 N (right) + 50 N (left) = 0 N resultant force on the car
move because the
pushing forces Forces and Their Effects 5
exerted on the car are
in opposite
directions.
They cancel out
each other. Hence,
the resultant force
would be 0 N.

Scenario 4 150 N pushing
Look at the picture below. Does the car move? force to the left
If it does, in which direction does the car move?

50 N pushing
force to the right

MarshallCoCpayvriegnhditsh
The car will move towards the left. Even though both persons are exerting
pushing forces on the car, the person on the left is exerting a pushing force
of only 50 N. The person on the right is exerting a pushing force of 150 N. Since
the forces are in opposite directions, they cancel out each other partly.
There is a resultant force of 100 N acting towards the left. Hence, the car moves
towards the left.

What will happen if the person on the left pushes with a force of 150 N
while the person on the right pushes with a force of 50 N? Will the car move?
In which direction will the car move?

Go to WB Activity 1.1

WOW!

The picture shows a
car compacter. The car
compacter can produce
a very large force to
crush a car into a flat
piece of scrap metal.

6 Chapter 1

Key Ideas Forces
can be a
push
MarshallCoCpayvriegnhditsh pull

whose effect can be

added together cancelled out completely partly cancelled out

to give rise to a
resultant force

Force and Motion Forces and Their Effects 7

1.3 Pressure

MarshallCoCpayvriegnhditshSubmarine at surface of waterSubmarine under water

When a submarine is submerged deep into the ocean, the walls of the
submarine experience hundreds of Newtons of liquid pressure per
square metre.

Submarine

The seawater exerts pressure on the submarine in all directions.

To resist the crushing pressure due to the weight of water, the walls of the
submarine must be specially constructed.

Pressure is the force exerted per unit area. This force can be exerted by

air or water. P= F
A
The unit for pressure is pascals (Pa)
or kilopascals (kPa). where P = pressure (Pa)

F = force (N)

A = surface area (m2)

8 Chapter 1

MarshallCoCpayvriegnhditsh
Earth’s atmosphere

Air pressure

Air pressure is the force exerted by air per unit area. The thin blue layer you see
above the Earth’s surface in the picture is the Earth’s atmosphere. This is mainly
made up of air. Even though air is relatively weightless in small quantities,
the weight of the entire column of air in the atmosphere pressing down on
a surface can be quite large!

The diagram below shows a column of air pressing down on a surface.
Imagine that the column of air reaches up into the atmosphere. The weight
of the entire column of air will be pressing down on a point on the ground.
This entire column of air pressing down on the surface gives rise to air pressure.

The higher from the ground we move, the smaller the column of air pressing

down. This would mean that pressure decreases as we move higher from

the ground. column of air

There is a smaller column of

air pressing down at point B.

There is a larger column Therefore, the pressure at point
of air pressing down B B is less.

at point A. Therefore,

the pressure at point

A is larger. A

Surface at ground level

Forces and Their Effects 9

MarshallCoCpayvriegnhditsh The higher we go up a mountain, the
smaller the column of air pressing down.
Hence, air pressure decreases as we move
higher up a mountain.
The low air pressure makes it difficult to
breathe. This is why mountain climbers
climbing tall mountains often have to carry
oxygen tanks to help them breathe.

Put on Your Thinking Cap

How do you think
a straw works? Why
does the water in the cup
enter your mouth when
you suck on the straw?

10 Chapter 1

Liquid pressure

Liquids also exert pressure as they have weight. Liquids are heavier than air.
This means that pressure exerted by liquids is much greater than pressure
exerted by air.

Liquid pressure is the force exerted downwards by a liquid per unit area.
It depends on the weight of the liquid above the point. The more liquid there
is above that point, the greater is the pressure. Look at the picture below.

At which point will the liquid pressure be greater?
MarshallCoCpayvriegnhditsh
The weight of the The diver at
water above point A is point B will
less than that above point B. A experience a
Therefore, the liquid pressure greater liquid
at point A is less. pressure.

B

Since point B is below point A, the liquid pressure at level B is greater than the
liquid pressure at level A. The diver at point B will experience a greater liquid
pressure.

This means that the deeper we go into the ocean, the greater the liquid pressure.

WOW! Go to WB Activity 1.2

The Mariana Trench is about 10 km below the surface of the
ocean. It is also the deepest point on Earth. The pressure there is
about. 1,000 times that of the air pressure at sea level.

Forces and Their Effects 11

Key Ideas

Pressure
can be

MarshallCoCpayvriegnhditshair pressure liquid pressure
due to due to

air above a surface liquid above a surface

12 Chapter 1

1.4 To float or to sink?

MarshallCoCpayvriegnhditsh
A ship made from iron floats on water but an iron block
of the same weight sinks when placed in water.

Why does a ship weighing hundreds of tons float on water while an iron block
of the same weight sink when placed in water?

Look at the cross-section of the hull of the ship and the iron block. What do
you notice?

Hull of ship

Iron block

Water

The hull of the ship pushes away more water than the iron block. This is
because the hull of the ship occupies more volume than the iron block.

We say that the hull of the ship displaces more water than the iron block.

Forces and Their Effects 13

The water that is displaced exerts an upward force on the object. This upward
force is known as assistance force (or upthrust).

Upthrust is larger than weight

MarshallCoCpayvriegnhditshHull of ship Upthrust is less than weight

Water Iron block

Weight Weight

The greater the volume of water displaced, the greater the upthrust. We can
also say that an object with a large volume has large buoyancy.

• When the upthrust is larger than the weight of the object, there is
a resultant upward force which keeps the object afloat.

• When the upthrust is less than the weight of the object, there is
a resultant downward force which causes the object to sink.

Going Further Go to WB Activity 1.3

Can we use concrete
to build a ship?

No! A v-shaped
concrete hull will
still be too heavy.
It cannot displace
enough water to
keep it afloat. As a
result, the concrete
ship would sink.

14 Chapter 1

Key Ideas

An object placed
in a liquid
will

floatMarshallCoCpayvriegnhditsh sink
if if

upthrust is larger upthrust is less
than weight than weight

Forces and Their Effects 15

1.5 Frictional force

What happens when Eddy pushes the toy car?
The toy car comes to a stop after some time. A force is applied on the toy car
to make it move. Do you think there was any force acting on the car to make
it slow down and stop?
A force that can slow down or stop a moving
object is known as frictional force. Frictional
force always acts in the opposite direction to
the movement of an object. Frictional force
opposes the motion of the object.

There is friction between the wheels of the toy car and the surface. This frictional
force acts in the opposite direction to the movement of the toy car. As a result,
the car slows down, then stops.
Push a toy car across two different surfaces: your table top and on a piece
of sandpaper. Make sure you push the car with the same force. Observe the
movement of the toy car. What do you notice?

Pushing force
MarshallCoCpayvriegnhditsh

16 Chapter 1 Frictional force

Table top Sandpaper

The toy car that is on the table top travels further than the toy car on the
sandpaper. This is because there is less friction on a smooth surface
compared to a rough surface.

Friction can be very useful. Friction between our shoes and the ground keeps us
from slipping. This allows us to move forward. If there was no friction, it would
be difficult to walk properly.
MarshallCoCpayvriegnhditsh
We can generate heat when we
rub our hands together.

Friction allows us to walk on the Friction can be used to generate heat.
ground without slipping. Forces and Their Effects 17

When we rub our hands together, they
will feel warm after a while. Friction can
generate heat.

However, friction can cause surfaces
to wear out.

Friction between the wheels of
the car and the ground eventually
causes them to wear out. The
wheels have to be changed,
otherwise driving could be
dangerous during rainy days.

Friction can cause
tyres to wear out.
MarshallCoCpayvriegnhditsh
Friction also generates unwanted heat that Inner
can cause the moving parts in machines tube
to become very hot. This causes them to
wear out more easily.

How can we reduce the wear and tear due to friction?

Engine oil can be used to reduce the
friction between the moving parts.

Engine oil

Ball
bearings

Ball bearings help to reduce
friction between two moving
surfaces. The ball bearings allow
the inner tube to turn freely.

18 Chapter 1

MarshallCoCpayvriegnhditsh Try This!

Take the cap of a jam jar and push it along the floor.
Is it difficult to move the cap?
Now, put enough marbles below the cap to allow the cap to roll on the marbles.
Push the cap along the floor. What do you observe?
The cap moves about much more easily! The marbles act like ball bearings to help
reduce friction.

Cap
Marbles

Go to WB Activities 1.4 & 1.5

Forces and Their Effects 19

Key Ideas

Frictional force
opposes motion

and is
MarshallCoCpayvriegnhditsh
useful not useful
as it as it

generates allows us to walk generates wears down
useful heat without slipping unwanted heat surfaces

20 Chapter 1

MarshallCoCpayvriegnhditsh Review Questions

1. W hat is the resultant force present when two boys are pushing with equal
strength on opposite sides of a box?

2. W hy is it important for submarine hulls to be built to withstand very high
pressures?

3. List two advantages of friction.

Experiment Time!

Can you estimate how much force is required to move an object over a rough
surface and over a smooth surface?
Process skills
observing, using apparatus and equipment, inferring, comparing, analysing, evaluating,
investigating
What you need
hanging spring balance, box filled
with books, raffia string
Procedure and observations
1. Tie the raffia string around the box.
2. Place the box on a smooth concrete surface.
3. Hook one end of the spring balance on the raffia string and pull the box towards

you. Record the reading on the scale of the spring balance.
4. Place the same box on a rough road surface and repeat step 3.
Conclusion
1. W hat difference did you observe when you pulled the box over the rough road

surface and the smooth concrete surface?
2. G ive a reason to explain the differences you observed.

Go to WB Revision Worksheet 1

Forces and Their Effects 21