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475 © Pearson Education Limited 2002Exploring Science for QCA Copymaster File 7

7K Quick Quiz

7

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7Ka

1 A force is:

A a spring. B an engine.

C a movement. D a push or a pull.

2 Which answer shows three non-contactforces?

A magnetism, gravity, friction

B gravity, friction, upthrust

C gravity, static electricity, magnetism

D upthrust, static electricity, friction

3 The unit of force is the:

A newton. B kilogram.

C gram. D metre.

4 A force can be measured using:

A a stop clock. B a ruler.

C a thermometer. D a force meter.

7Kb

1 A boat will float because:

A gravity does not work over water.

B it is built out of light materials.

C upthrust pushes against its weight.

D it has air inside it.

2 Density is:

A the weight of a fixed mass ofsomething.

B the volume of a fixed weight ofsomething.

C the weight of a fixed volume ofsomething.

D the mass of a fixed volume ofsomething.

On your answer sheet, circle the correct letter for each question.

3

You can find the volume of the object inthe can by:

A measuring the object and multiplyingthe numbers.

B measuring the volume of water itdisplaces.

C weighing the object.

D using a thermometer.

4 The density of water is 1 g/cm3. Which ofthese objects will float in water?

A density = 2 g/cm3

B weight = 2 N

C density = 0.5 g/cm3

D mass = 1 g

7Kc

1 An elastic material:

A does not stretch.

B stretches and stays in its new shape.

C stretches and then goes back to itsoriginal shape.

D cannot be squashed.

2 What are the units for weight and mass?

A weight – newtons;mass – kilograms

B weight – kilograms;mass – newtons

C weight – kilograms;mass – kilograms

D weight – newtons;mass – newtons

displacement can

measuring cylinder


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3 Which is true?

A Your weight would be the same on theEarth and on the Moon.

B Your mass would be the same on theEarth and on the Moon.

C Your weight would be more on theMoon than on the Earth.

D Your mass would be less on the Moonthan on the Earth.

4 What do most force meters have insidethem?

A a light bulb B a spring

C wires D a battery

7Kd

1 Which of the following sentences aboutfriction is not correct?

A Friction can make an object get hotter.

B Friction wears car tyres away.

C Friction slows down a ball rolling ingrass.

D Friction can speed up a falling object.

2 Which of these would produce the mostfriction when they rub together?

A a rough surface and a smooth one

B two smooth surfaces

C two rough surfaces

D two smooth surfaces with oil betweenthem

3 Which example shows unhelpful friction?

A friction between a tyre and the road

B friction in the wheel axles of a bicycle

C friction between paper and the point ofa pencil

D friction between your shoes and thefloor

4 Which of the following is not an exampleof a lubricant?

A grease for bicycle chains

B rubber on car tyres

C water on swimming pool tiles

D oil in a car engine

7

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7K Quick Quiz (continued)

7Ke

1 The speed of a car is a measure of how it is travelling. Which is the missing

word?

A far B fast

C long D high

2 If a car goes faster:

A the thinking distance does not change.

B its stopping distance increases.

C its braking distance does not change.

D its braking distance gets less.

3 Which of these factors will help a car tostop quickly?

A a tired driver

B going uphill

C worn tyres

D a wet road

4 This graph shows the distance moved bysomeone catching a bus.

Dis

tan

ce (

m)

Time (min)0

80

70

60

50

40

30

20

10

042 6 8

ab

cd

e f

Which part of the graph shows the personwaiting at the bus stop?

A a to b B b to c

C c to d D d to e

Name Class


7K Target Sheet

7

K

Topic Targets Before the unit I have learned this I have revised this7Ka 1 Know what a force is.

2 Know about contact and non-contact forces and be able to name some examples.

3 Know what the unit of force is.

4 Know how to measure a force.

7Kb 1 Know about the forces on a floating object.

2 Know the meaning of density.

3 Know two ways of measuring the.volume of an object.

4 Be able to predict whether an objectwill float.

7Kc 1 Know what an elastic material is.

2 Know the difference between mass and weight, and know their units.

3 Know that weight can change depending on where you are.

4 Know how a force meter works.

7Kd 1 Know what friction is.

2 Know how rough and smooth surfaces affect friction.

3 Know some examples of helpful friction and unhelpful friction.

4 Know how that lubricants reduce friction.

7Ke 1 Know what is meant by speed, and know the units for speed.

2 Know how the stopping distance ofa car depends on speed.

3 Know some of the factors that affectthe stopping distance of a car.

4 Know how to interpret simple distance / time graphs.


Page 1 of 2

7

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7K Word Sheets

Word sheets that include new words from the ‘Focus on:’ pages are available on theExploring Science website.

Word Pronunciation Meaning

air resistance A force that tries to slow things down that are moving through air. It is a type offriction.

contact force A force that needs to touch an object before it can affect it (e.g. friction).

drag Air resistance and water resistance are both sometimes called drag.

force A push or a pull.

force meter Piece of equipment containing a spring, used to measure forces.

friction A force that tries to slow things down when two things rub against each other.

gravity The force of attraction between any two objects. The Earth is very big and so has strong gravity that pulls everything down towards it.

magnetism A force that attracts objects made out of iron.

newton (N) The unit of force.

newton meter Another name for a force meter.

non-contact force A force that can affect something from a distance (e.g. gravity).

speed How fast something is moving. Often measured in metres per second (m/s).

static electricity A force which attracts things with extra electrical charges on them.

upthrust A force that pushes things up.

water resistance A force that tries to slow things down that are moving through water. It is a type offriction.

7Ka – The forces are with us


density The amount of mass that 1 cm3 of a substance has. Measured in g/cm3.

displacement The volume of water pushed out of the way by an object.

upthrust A force that pushes thing up.

7Kb – That floating feeling

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7K Word Sheets (continued)

7

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air resistance A force that tries to slow things down that are moving through the air. It is a type offriction.

friction A force that tries to slow things down when two things rub against each other.

lubricant loo-brick-ant A substance (normally a liquid) used to reduce friction.

lubrication loo-brick-ay-shun Adding a lubricant to something.

water resistance A force that tries to slow things down that are moving through water. It is a type offriction.

7Kd – Friction


braking distance The distance a car travels while the brakes are trying to stop it.

distance/time graph A graph that shows how far and how fast something travels during a journey.

kilometres per Units for speed when the distance is measured in kilometres and the time is measured hour (km/h) in hours.

metres per Units for speed when the distance is measured in metres and the time is measured second (m/s) in seconds.

miles per hour (mph) Units for speed when the distance is measured in miles and the time is measured in hours.

speed How fast something is moving. Often measured in metres per second (m/s).

stopping distance The distance a car moves while it is stopping. The stopping distance is equal to thethinking distance and the braking distance added together.

thinking distance The distance a car travels while the driver is deciding to press the brake pedal.

7Ke – The need for speed


balanced forces When two forces are the same strength, but working in opposite directions.

elastic Any substance that will return to its original shape and size after it has been stretchedor squashed.

gram A unit for measuring mass (g).

gravity The force of attraction between any two objects. The Earth is very big and so has alarge gravity pulling everything down towards it.

kilogram A unit for measuring mass (kg). There are 1000 g in 1 kg.

mass The amount of matter that something is made of. Measured in grams (g) and kilograms (kg). Your mass does not change if you go into space or to another planet.

newton The unit of force (N).

stationary Not moving.

unbalanced forces When two forces working in opposite directions are not the same strength.

weight The amount of force with which gravity pulls something towards the Earth. It ismeasured in newtons (N).

7Kc – Balancing act/Hooked!/Weighing in


Page 1 of 3

7K End of Unit Test

Name Class

1 Fill in the gaps. Choose words from the box. You will not need to use all the words.

a A force can be a or

.

b Forces can change the ,

or

of things.

[4 marks]

2 a Write down one example of useful friction.

b Write down one example of when friction is not useful.

[2 marks]

3 a How can you increase the friction between two surfaces?

b Write down two ways that you can reduce the friction between two surfaces.

[3 marks]

4

7

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colour direction

flavour pull push

shape speed

A B C

a Which picture shows balanced forces?

b What will happen to the speed of the car?

c What will happen to the speed of the boat?

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7K End of Unit Test (continued)

d What is causing force X?

e Why doesn’t a rocket in space need to use its engine to keep moving?

[5 marks]

5 This boat is not moving. Thereare no horizontal forces on it. Draw and label two forces acting on the boat.

7

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[2 marks]

6 What are the units for weight?

[1 mark]

7 Tick the correct statements.

A Mass is the amount of substance in something.

B Weight is the amount of substance in something.

C Your mass would be the same on the Earth and the Moon.

D Your weight would be the same on the Earth and the Moon.

E Mass is a force.

[2 marks]


Page 3 of 3

7K End of Unit Test (continued)

8 An object has a mass of 5 g and a volume of 10 cm3.

a What units would you use for density?

b What is the formula for working out density?

7

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density = ————————

c What is the density of the object? Show your working.

[3 marks]

9 Rizwan cycled to his friend’s house. This distance/time graph shows his journey.

Time (minutes)0 10 20 30 40 50 60

0

5

4

3

2

1

Dis

tan

ce (

mil

es)

a How far is it from Rizwan’s house to his friend’s house?

b Rizwan cycled down a steep hill on his journey. Label the part of the graph

that shows him cycling fast down the hill.

c Rizwan stopped for a rest during his ride. How long did he stop for?

[3 marks]

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7K Summary Sheets

Forces are pushes or pulls.

Forces can:

� change the shape or size of an object� change the speed things are moving (make them move faster or slower)� change the direction of a moving object.

The units for measuring force are newtons (N).

Friction is a force caused by two things rubbing together. Air resistance and waterresistance are kinds of friction. They are sometimes called drag.

Upthrust pushes things up. Solid things, like your chair, give you upthrust. Thingsfloat in water because of upthrust.

Contact forces need to touch the thing that they are affecting. Examples of contactforces are:

� friction� air resistance� water resistance� upthrust.

Some forces do not need to touch the thing that they are affecting. They are callednon-contact forces. There are three non-contact forces:

� magnetism� gravity� static electricity.

Balanced forces

7

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A rocket in space does not need to use its engine to keep moving. There is no air inspace, so there is no air resistance to slow it down.

upthrust

downward forcefrom string

The upwards and downwards forces on this balloon are balanced.The balloon will not move.

The forces here are balanced. The girl will not move, and neither willthe wall!

Forces and their effects


Page 2 of 3

7K Summary Sheets (continued)

If you are floating in a swimming pool, your weight and the upthrust are balanced.

7

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Density and floatingYou can decide if something will float by working out its density. Density is the massof a certain volume of something, and it can be calculated using this formula:

density =

The units for density are g/cm3.

The density of water is 1 g/cm3. If an object has a density less than 1 g/cm3 it will float.If its density is greater it will sink.

Measuring forcesElastic materials will stretch with a force and then returnto their original shape when the force is taken away.

Materials like Plasticine will stretch with a force but theywill not return to their original shape afterwards.Plasticine is not elastic.

Springs are used to measure the size of a force becausethey are elastic. A big force stretches a spring further thana small force. Force meters have springs inside them.

Weight and massYour mass is the amount of substance in your body. Your mass is measured inkilograms (kg).

Your weight is a force caused by gravity pulling on your body. The newton (N) is thescientific unit used to measure forces, and so it is also used as the unit for weight.

Wherever you take an object, its mass will not change but its weight depends on theforce of gravity. An object on the Moon would have a smaller weight than on Earth,because the Moon’s gravity is not as strong as Earth’s.

On Earth, gravity pulls on every kilogram of mass with a force of 10 N.

massvolume

upthrust

weight (gravity)

0

1

2

4

3

5

N

This force meteris measuring a

force of 1 N.

240

7K

Exploring Science for QCA Teacher’s Guide 7 © Pearson Education 2002

7K Mark schemes

Quick QuizQuestion Answers Marks

Topic 1 2 3 4

7Ka D C A D 4

7Kb C D B C 4

7Kc C A B B 4

7Kd D C B B 4

7Ke B B B C 4

End of Unit TestQuestion Level Answers Mark scheme

1 2 a Push, pull 1 mark – answers either way round3 b Shape, speed, direction 3 marks – 1 for each one correct, answers in any order

2 4 a any example of useful friction (e.g. shoes on floor, 1 marktyres on road)

4 b any example of friction not being useful (e.g. in an 1 markengine, axles)

3 4 a Increase roughness of surface or use high friction 1 markmaterial (e.g. rubber)

4 b Make surfaces smoother; 1 mark5 use a lubricant 1 mark – accept ‘use oil’ or similar answer

4 5 a C 1 mark5 b Slow down 1 mark – accept equivalent answers5 c Speed up 1 mark – accept equivalent answers5 d Water resistance 1 mark6 e No friction in space to slow it down, so speed 1 mark – �� mark for each point or any sensible equivalent

will stay the same

5 5 Equal sized up and down arrows drawn 1 mark5 Upthrust and gravity (or weight) correctly labelled 1 mark

6 5 Newtons 1 mark

7 6 A ticked 1 mark – no marks if B also ticked7 C ticked 1 mark – no marks if D also ticked; remove one mark if E ticked

8 7 a g/cm3 1 mark7 b Mass ∏ volume 1 mark if both correct6 c Numbers substituted correctly and correct answer 1 mark – �� mark for substitution, �� mark for correct answer

(0.5 g/cm3)

9 5 a 4.5 miles 1 mark – �� mark if no units or incorrect units7 b Section of graph between 50 and 1 mark

54 minutes labelled6 c 6 minutes 1 mark

Matching End of Unit Test marks to NC levelsLevel Marks Cumulative Suggested

available total threshold toachieve level

2 1 1 1

3 3 4 3

4 4 8 5

5 9 17 12

6 4 21 17

7 4 25 22

FrictionFriction is a contact force. Friction can:

� slow things down� wear things away� produce heat� make a noise.

Friction is sometimes helpful, for instance: Friction is not always helpful:

� your shoes grip the floor because � parts of engines wear away because of friction of friction

� tyres and brakes use friction � friction makes bicycles harder � pencils write because of friction. to pedal.

Friction can be increased by using rough surfaces, or by using materials like rubberthat have a lot of friction.

Friction can be reduced by using smooth surfaces, or by lubrication. Things like oil orgrease are lubricants, and help things to move past each other easily.

SpeedTo measure how fast something is travelling you need to measure the distance ittravels and the time taken. Units of speed are km/h or m/s or mph. The units for speed depend on the units you have used to measure the distance and the time.

Stopping distancesA moving car takes some time to stop. The distance it travels while the driver isdeciding whether to stop is called the thinking distance, and the distance it travelswhile it is slowing down is called the braking distance. If you add the two distancestogether you get the stopping distance.

Stopping distances are longer if the road is wet or icy, if the car has worn tyres, or if the driver is tired or has been drinking alcohol.

Distance/time graphsA journey can be shownon a distance/time graph.This graph shows a personrunning, then stopping fora rest, then walkingslowly. The steeper theline on the graph, thefaster they are moving.

Time (minutes)

0 10 20 30 400

3

2

1Dis

tan

ce (

km

)

Page 3 of 3


7K Summary Sheets (continued)

7

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Page 1 of 2

7Ka/1 Forces in action

Name Class

7

K

a

P Fill in the gaps on this sheet. The words you need are given in the brackets.

Apparatus� 2 magnets

Apparatus� ice cube� wooden block

1

The magnets are (attracting/repelling) each other.

The force is strongest when the magnets are (close

together/far apart). The name of this force is

(friction/gravity/magnetism).

What will happen if you turn one of the magnets round?

2

The force of (friction/gravity/magnetism) tries to stop

the blocks moving across the desk.

It is (easier/harder) to push the block of ice, because

the ice is (smoother/rougher).

ice

wood

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7Ka/1 Forces in action (continued)

7

K

a

observingS

Apparatus� spring

Apparatus� force meter� object

Apparatus� Two sheets of

paper

P

0

1

2

4

3

5

Apparatus� natural string� plastic string

3

It is (harder/easier) to tie a knot in the plastic string.

The plastic string has a (rough/smooth) surface so

there is less (friction/gravity/magnetism).

4

The force from the spring gets (bigger/smaller) if it is

stretched further. The spring is (pulling/pushing).

5

Weigh the object.

How much does your object weigh?

The force of (friction/gravity/magnetism) is pulling the

object downwards.

6

The paper takes (less time/more time) to fall if it is

crumpled up. The air resistance is (more/less) when

the paper is crumpled up.


7Ka/2 Contact and

non-contact forces

Name Class

7

K

a

1 Cut out the five pictures and five labels at the bottom of the page.

2 Stick the forces in the correct boxes.

3 Stick the correct label below each picture.

knowledgeS

Magnetism Staticelectricity

Friction Gravity Upthrust

Non contact forces

Contact forces

✄


7Ka/3 Forces are

everywhere

Name Class

7

K

a

1 Which forces are pushes and which ones arepulls? Write the correct words in the spaces.

?

2 Look at the pictures below. Write the names of the forces next to the arrows.

3 Which pictures show non-contact forces?

4 Complete these sentences.

a A is needed to start an object moving.

b A force can change the , and

of an object.

c Nothing starts to move without a being involved.

d Three forces which can act from a distance are ,

and forces.

knowledgeS

A

D

B

E

C

F


7Ka/4 Find the forces

Name Class

7

K

a

Write the answers to the clues in the spaces.

Clues Answers

a A force which pulls you down.

b This force helps to hold things to fridge doors.

c This type of force needs to touch something to affect it.

d This force rubs things away.

e This force helps a ship float.

f A form of electricity which can attract things.

Now try to find the words in the wordsearch. Mark all the contact forces in redand the non-contact forces in blue.

(Use pen and pencil if you do not have any coloured pencils.)

?

knowledge, literacyS

W F R I C T I O N

S R A O P D Y Q L

A F C H R T Y U M

S T E O I U F S J

I S I V N P I T P

D V A R E T I O M

B R N I E H A I E

G I K N O R U C L

R C G D I U E M T

S A I B O S K F U

M F S T A T I C Z


7Ka/5 Which way is the

force acting?

Name Class

7

K

a

Mark the diagrams with arrows to show the forces. Most of the pictures havemore than one force. Write in the name of each force.

Think about whether the forces are balanced or not. When you draw arrowsto show balanced forces, both arrows should be the same size.

If the forces are unbalanced, the biggest force should have the biggest arrow.

The first one has been done for you.

?

knowledgeS

magnetismA

C

D

B

FG

I

E

H


7Ka/6 Bathroom scales

7

K

a


How do bathroom scales work? There is no space inside for a long spring, like the ones in force meters. And how does the dial go round? Scales measure your weight, which is the force of gravity pulling on you.

This diagram shows a simplified version of what happens inside a set of bathroomscales. Real scales are a bit more complicated than this. They need more bits andpieces to make sure that everything fits into a fairly small, flat case.

400

When you stand on the scales you are pushing down on a lever that is attached to thespring. The lever and spring are arranged so that you do not make the lever movevery far – this is so everything can fit inside a small case. The end of the lever moves arack, which is a long piece of metal with teeth along one side. The rack is touching apinion, a wheel with teeth on it. The pinion is attached to a round dial which has theweights marked on it. When the rack moves down, it turns the pinion, which turnsthe dial. When you stand on a set of scales you can see the dial moving. The numberon the dial that ends up under the pointer shows your weight. Most bathroom scalesturn your weight into a reading of your mass in kilograms.

1 a What is the name of the force that is pulling you down when you standon a set of bathroom scales?

b Is this a contact force or a non-contact force?

2 What is the weight of the person standing on these scales?

3 If a heavier person stood on the scales:

a would the spring be stretched more or less than it is now

b would the rack move up or down?

4 Do you think the spring in the bathroom scales is harder to stretch than theones in the force meters you use in school? Explain your answer.

5 These scales will weigh someone as heavy as 1300 N. How could the scales bechanged so that they could weigh a heavier person?

6 You want to weigh your baby sister, but she is too young to be able to standon the bathroom scales. How could you weigh her using the scales?

?

N

010

020

0

300 400 500

600700

800900

100011001200

1300

pinion

rack

pointer

spring

lever

pivot

weight ofperson

of 2


7Kb/1 Floating, sinking

and density

7

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b

Is there a connection between the density of an object and whetherit floats or sinks?

Density measures how much mass there is in 1 cm3 of something. You have towork it out from a mass and a volume.

P

Apparatus� Different materials � Bowl� Ruler � Water� Calculator � Balance

Method

1 Make a table for your results, like this:

2 Choose a material, and write its name in your table.

3 Use a balance to find its mass, and write it in your table.

4 Measure the length, height and width of your material, like this:

Write the measurements in your table.

5 Multiply the three measurements to find the volume of your material.

6 Divide the mass by the volume you have just worked out. This is the density.Write it in the correct column.

7 Now see if your material floats or sinks. Write F or S in the last column.

8 Repeat steps 2 to 7 for other materials.

9 Write two or three sentences to describe what you did.

Material Mass Length Height Width Volume Density Floats

(g) (cm) (cm) (cm) (cm3) (g/cm3) or Sinks?

01

23

45

67

89

10

height

length

width


Page 2 of 2

7

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b

7Kb/1 Floating, sinking and density

(continued)

observing, numeracy, consideringS

Considering your results/conclusions1 Look carefully at your results. Do materials with high densities float or sink?

2 Copy and complete these sentences. Choose from the words in thebrackets.

Density is a way of saying how much (mass/volume) there is in 1 cm3 of amaterial. A material with a high density feels (lighter/heavier) than amaterial with a low density.

Materials with a high density (float/sink) when you put them in water.

Materials with a (high/low) density float.

The density of water is 1 g/cm3. If a material has a density (less/greater)than the density of water, it will float.


7Kb/2 Upthrust in

different liquids

7

K

b

Does the amount of upthrust depend on the liquid?You are going to find out if the amount of upthrust depends on the liquid.Even objects that sink have upthrust acting on them, but the upthrust is notbig enough to make them float.

You can measure upthrust by finding out how much the weight of an objectchanges when you put it in water.

Method

1 Write a method for your investigation. Remember to say how you will make sure that your investigation is fair.

Recording your results

2 Make a results table like this:

3 Carry out the experiment and fill in your table. You calculate the number in thefourth column using this formula:

Upthrust = weight in air – weight in liquid

4 You can find out more about your liquids using a balance. Measure out equalvolumes of each liquid and find their mass. Work out the density and write yourresults in the last column of your table.

Considering your results/conclusions

5 Does the upthrust depend on the kind of liquid?

6 What is the connection between the density of the liquid and the amount ofupthrust it provides?

planning, observing, consideringS

Apparatus� Force meter � Different liquids� String � Beaker� Object � Balance

Liquid Weight in air (N) Weight in liquid (N) Upthrust (N) Density of liquid (g/cm3)


7Kb/3 Floating questions 1

Name Class

7

K

b

1 Josh was in the sea at high tidewhen he came across a large stone under the water. He tried to lift the stone and was surprised to find that he could move it easily. He returned at low tide and found the stone out of the water. This time he could hardly move it.

Use the words in the box to complete these sentences. Some words can be used more than once.

a The stone felt lighter when it was under

. This is because

was helping to push it up.

b The stone does not float because its

is greater than the .

c The two forces which affect the stone are

and .

2 This is Danny floating in the water. Label the two forces.

?


gravity

upthrust

water

weight

3 Your weight is 600 N and you have just finished building a raft whichweighs 1000 N.

a What is the total weight of you and the raft?

b What is the smallest upthrust force needed so that it will just float with

you on it.


7Kb/4 Floating questions 2

7

K

b

1 What force holds a hot air balloon in the air?

2 Your weight is 600 N and you have just finished building a raft which weighs 1000 N.

a What is the total weight of you and the raft?

b What is the smallest upthrust force needed so that it will just float withyou on it.

?

3 The pictures below show objects that have just been placed below thesurface of the water. The arrows show the direction and size of the forcesaffecting each object.

a Which object will sink?

b Which object will just float in the water?

c Which object will float well and be able to carry a small load?

4 The table shows the masses and volumes of pieces of different materials.Copy the table, and complete the last column.Remember the formula for calculating density is:

Density = massvolume

knowledge, numeracyS

X Y Z

Material Mass (g) Volume (cm3) Density

Copper 1800 200

Wood 900 1500

Lead 567 50

Iron 790 100

Water 1000 1000

Polythene 690 750

Glass 197 80

Plasticine 26 20

Bone china 42 15

Brick 3200 2000

5 Make a list of all the materials in the table that will float.


7Kb/5 The Plimsoll line

7

K

b

This story started about two hundred years ago in the early days of the Britishmerchant navy. Greedy ship owners would often overload the ships with goods theywanted to sell in far-away countries.

Because they were so overloaded, manyships would sink if they met a storm atsea. The sailors’ families had to wait formonths before they knew if the crew hadsurvived the trip. Many never came back –they were ‘missing, presumed lost’.

In 1870, a member of Parliament calledSamuel Plimsoll decided that too manyships were being lost at sea due tooverloading. He passed a law forcing shipowners to have a special line painted onthe side of each ship. Loading of the shiphad to stop as soon as the water levelreached this line. If the water level wentabove the line, the ship owners would befined or imprisoned.

The ‘Plimsoll line’ is still in use today and can be seen painted on the side of all cargoships. Ships also have load lines for different parts of the world. These are veryimportant for ships which travel from the cold seas of Britain to the warmer tropicalseas. Warm sea water produces slightly less upthrust than cold sea water, so ships floatlower down in warm water. Fresh water also produces less upthrust than sea water.

literacy, knowledgeS

1 Why did ship owners want to overload their ships?

2 Why was this dangerous?

3 What did Samuel Plimsoll force ship owners to do?

4 Why was it dangerous for a fully loaded ship to travel from the seainto a fresh water river?

5 There are two reasons why tropical fresh water produces lessupthrust than water in winter in the North Atlantic. What are they?

6 A fresh egg is floating in a cup of water. You add lots of salt to thewater in the cup. How does this affect the way the egg floats?

?

Plimsoll LineTF

FTSW

WNA

Load lines If a ship wasloaded to herein the summer,the water wouldonly come up tohere in the winter.

TF Tropical Fresh WaterF Fresh WaterT Tropical Salt WaterS Summer

W WinterWNA Winter North

Atlantic


7Kb/6 Archimedes

7

K

b

Archimedes lived in Syracuse, Italy, and was a great inventor and philosopher. One ofthe scientific facts that he discovered is called Archimedes’ Principle. The upthrust onsomething in a fluid is equal to the weight of fluid displaced.

1 a What is the weight of the stone?

b What is the upthrust on the stone when it is in the water?

c What is the weight of the water in the small beaker?

d Why doesn’t the stone float?

2 If you compared the weight of the stone in air with its weight in water, the difference would be the weight of the water displaced by the stone. This difference is the upthrust.

a What is the weight of the wooden block?

b What is the upthrust on the block?

c What is the weight of the water in the small beaker?

d Why does the wooden block float?

?

a Which object is the heaviest? How do you know?

b Write the three objects in order of their weight, starting with theheaviest. Explain how you worked out your answer.

4 a What would happen if you put a 1 N weight on top of block Z?

b What would the extra water in the small beaker weigh?

5 Some of the things Archimedes invented are still in use today. Find outwhat an ‘Archimedes screw’ is and what it is used for.

knowledge, numeracy, researchS

This volumeof liquid is the

same as thevolume of the

stone.

34567

678910

01234

012

X Y Z

3 All the beakers have water in them.


Page 1 of 2

7Kc/1 Make a force meter 1

7

K

c

Method

1 Set up your apparatus like this:

P

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

2 Measure the position of the bottomof the spring. You can use anotherruler to help you. Write your resultin the table. Hang the holder on the spring andmeasure the length again. The holderhas a mass of 100 g. Write yourresult in the table.

3 Put more masses on the spring and measure its length each time.

Mass Weight Length of spring

(g) (N) (cm)0 0

100 1

200 2

300 3

400 4

500 5

Apparatus� Stand and 2 clamps � Mass holder and masses� Metre rule � G clamp� Spring � Objects to weigh


1 Make a copy of this table and fill it in.

of 2


7Kc/1 Make a force meter 1 (continued)

7

K

c

2 Plot a graph of your results on graph paper. You will need to use axes likethese:

3 Now you can use your force meter to weigh other things. Hang an object onthe spring and measure its length. Then use your graph to find its weight, like this:

observing, presenting, consideringS

Len

gth

of

spri

ng

(cm

)

0 1 2 3 4 5Weight (N)

Len

gth

of

spri

ng

(cm

)

Weight (N)

This is the length you measured.

This tells you theweight of the object.


7Kc/2 Make a force meter 2

7

K

c

You can use a spring to make a force meter. Before you can weigh anything you need to calibrate it. This means you find out how much the spring stretches for particular weights.

Method

1 Set up your apparatus like this:2 Draw a table for your results, like this:

P

Your teacher will tell you how many different masses to use.

3 Measure the length of the spring without anything hanging on it. This is themeasurement for zero mass.

4 Add masses and measure the length of the spring each time.

5 Fill in the weight column of your table. Weight = mass ¥ 10.

6 Work out the extension of the spring for each weight. The extension is thelength of the spring minus the length for zero mass.

7 Plot a graph of weight (along the bottom) and extension (up the side).

8 Now you can use yourforce meter to weighother things. Hang anobject on the spring andmeasure its length. Workout the extension andthen use your graph tofind its weight, like this:

Apparatus� Stand and 2 clamps � Mass holder and masses� Metre rule � G clamp� Spring � Objects to weigh


Mass Weight Length Extension

(g) (N) (cm) (cm)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

Exte

nsi

on

(cm

)

Weight (N)

This is the extension you measured.

This tells you theweight of the object.


7Kc/3 What do forces do?

Name Class

7

K

c

1 Look at the four pictures below. The size of the arrow represents thesize of the force and its direction.

For each picture fill in the gaps.

?

knowledgeS

The forces

are

(balanced/unbalanced).

The forces

are


The forces are


The car

(will/will not) move.

This force is called




The forces are


The (boy/girl)

will win the contest.

A

B

C

D


7Kc/4 The size of a force

Name Class

7

K

c

1 The unit of force is called a .

2 The pictures below show examples of forces. Write thecorrect size of each force in the space below each picture.Choose numbers from the box.

?

knowledgeS

3 Fill in the missing words:

The Earth all objects towards it. This force is called

. It is this force which gives us .

4 Complete these sentences using words from the box:

The weight of a 2 kg mass on Earth is .

The typical mass of a man on Earth is about .

The unit of mass is the .

The unit of force is the .

The mass of a 2 kg bag of apples on the Moon

is .

kilogram

newton

20 N

2 kg

80 kg

50 000 000 N

0.5 N

650 N

10 N


7Kc/5 Stretch, stretch,

stretch and …

7

K

c

Matilda and Ravi carried outan experiment in class whichshowed how a spring wasextended (stretched) bydifferent forces.

They wrote this conclusion:

This experiment shows that a spring stretches by the same amount each time a 100 g force is added tothe other weights.

Mass (g) Weight (force) (N) Extension (cm)

0 0 0

200 2 4

400 4 8

600 6 12

800 8 16

1000 10 20

1 Plot a graph of their results on graph paper. Put weight on the horizontal axis.

2 Imagine that you make a force meter with this type of spring. What range offorces could you measure?

3 Ravi used his force meter to weigh some other objects. He wrote down theextension of the spring when he hung each object on it:

?

Work out the weight of each object using your graph.

4 Matilda and Ravi made mistakes in their conclusion. What were they?

Object Extension

A 2.0 cm

B 19.0 cm

C 4.5 cm

D 6.5 cm

knowledge, presenting, consideringS

Their results are shown in the table below.


Page 1 of 2

7Kc/6 Climbing ropes

7

K

c

Rock climbers and mountaineers use ropes to stop them getting hurt if they fall, butdid you know that climbing ropes are stretchy?

1 What force or forces are acting on the falling climber in picture B?

2 a What forces are acting on the climber in C?

b Are the forces balanced or unbalanced?

c What will happen to the falling speed of the climber?

3 Are the forces balanced or unbalanced in D? Balanced forces do not changethe speed of something that is moving.

?

Think about a spring like this chest expander. It is quite easy to stretch it a little way,but it takes a much bigger force to stretch it a long way. The amount of force from thespring depends on how far it has been stretched.

The same thing happens with climbing ropes.

A B C D

of 2


7Kc/6 Climbing ropes (continued)

7

K

c

knowledge, considering, researchS

4 a Will the climber fall further than the point she has already reached in D?Explain your answer.

b What will happen to the force from the rope if she falls further?

c What effect will this have on her speed?

5 a If she had a stretchier rope than the one shown, would she fall further ornot as far?

b What would happen if the rope was too stretchy?

6 In the example shown above, the force on the climber from the ropeincreases gradually.

a What would happen if the rope was not stretchy?

b What would it feel like if a non-stretchy rope stopped her fall?

7 Find out how belayers use friction to help them to hold onto the rope.

?


Page 1 of 2

7Kd/1 Materials and

friction 1

Name Class

7

K

d

What is the best material for wearing on a playground slide?Slides are more fun when you can go fast. To go fast the friction between you

and the slide must be as (big/small) as possible.

Apparatus� Squares of different types of materials � Force meter� Wooden block with a hook � Large mass (about 500 g)� 4 drawing pins

Method

1 Attach the first piece of material to the block using the drawing pins, like this:

2 Attach the force meter to the block.

3 Put the mass on top of the block.

4 Gently pull the block and material along the bench surface. Read the force meter, and write down the force needed to pull it.

5 Pull the block twice more, and write the results in the table. Calculate themean force needed.

6 Repeat steps 1 to 5 for other materials.

P

Material Force needed to pull block (N) Mean force

1st pull 2nd pull 3rd pull (N)

Find themean byadding upall threeresults, thendivide youranswer by 3.

Show your results in a bar chart.

0124 35679 810


of 2


7Kd/1 Materials and friction 1 (continued)

7

K

d

Considering your results/conclusions

It took the biggest force to pull the block with on it.

This material has the (most/least) friction.

It took the smallest force to pull the block with on it.

This material has the (most/least) friction.

If I wanted to go fast down a slide, I would wear clothes made

from .



7Kd/2 Materials and

friction 2

7

K

d

What is the best material for wearing on a playground slide?Slides are more fun when you can go fast.

1 Would you need to wear clothes that gave high or low friction? Explain your answer.

4 Test different materials, and work out the mean force needed to pull each one.

5 Present your results in a bar chart.

Considering your results/conclusions6 Write a conclusion for your experiment. Say which material produced the most

and least friction, and which one you would choose to wear to go fast on a slide.

Evaluation7 Is there any way that you could have improved your investigation?

Planning

2 Describe how you would carry out an experiment to find out which materialwould be best for wearing on a slide. Remember to explain how you will makesure your investigation is fair.


3 To get more accurate results, you should test each material three times and findthe mean force. Your table of results should look like this:

P

planning, observing, presenting, considering, evaluatingS

Apparatus� Squares of different types of materials � Force meter� Wooden block with a hook � Large mass (about 500 g)� 4 drawing pins

Material Force needed to pull block (N) Mean force

1st pull 2nd pull 3rd pull (N)

0124 35679 810


7Kd/3 Friction – true

or false?The statements below are all about friction. Some are true, some are false, and someare partly true.

1 Cut out the statements. Work in a group to sort them into three piles, and makesure you know why you have put each statement in a particular pile.

2 Make a table in your book to show examples of useful friction, and examples ofwhen friction is not useful.

7

K

d

knowledgeS

Friction always slows things down.

True False Partly true

Cars need friction to keep moving.

Cars need friction to stop. You could not walk without friction.

Friction is useful to gymnasts. Matches light because of friction.

Friction is useful to ships. Shoelaces stay tied up because offriction.

You could not pick up a cup of teawithout friction.

You could drink from a glass withoutfriction.

Snow increases the friction betweenyour shoes and the ground. Friction is useful in playgrounds.

Pencils do not need friction to write. There is no friction when you are rollerskating.

© Pearson Education Limited 2002Exploring Science for QCA Copymaster File 7

Name Class

7

K

d

512

7Kd/4 Friction around us

1 Copy the sentences and fill in the missing words.The words you need are in the box.

Friction is a caused by two

moving over each other. surfaces produce more

friction than surfaces.

2 Look at these diagrams. Put a circle around the all the places where there is friction. One has been done for you.

? force rough

smooth surfaces

3 Look at these pictures.

knowledgeS

You pull the block along all of these surfaces.

a It will be easiest to pull the block along the .

This is because it has the (smoothest/roughest)

surface, so there will be the (most/least) friction.

b It will be hardest to pull the block along the .

This is because it has the (smoothest/roughest)

surface, so there will be the (most/least) friction.

sandpaper

cork tile

lab bench polished table

block


7

K

d

513

7Kd/5 What’s rubbing?

7

K

d 1 Copy these sentences and fill in the gaps.

Friction is a caused by two moving over each other. surfaces produce more friction than surfaces.

Friction can be helpful, because it stops us when we walk, and that slow down cars or bicycles could not work without friction.

Friction is not always useful. It can cause and , and away things that rub against each other.

Oil can reduce the amount of . Oil stops the surfaces touching each other.Liquids that reduce friction are called .

2 Look carefully at these pictures.

?

knowledgeS

For each picture:

a Describe where there is friction.

b Say whether the friction is helpful or unhelpful.

c Describe how the friction could be increased or decreased.

For example:

A There is friction between the girl’s trousers and the grass. This is useful friction because it stops her sliding down the hill. She could increase this friction by wearing a rougher material.

A B C

D E


7Kd/6 Lubrication

7

K

d

?

1 a Which parts of the bike should the girl oil? Explain why.

b You should never put oil on the wheel rim where the brake blocks touch it.Explain why not.

c The girl going uphill is working very hard. What forces is she pushing against?

d There are two forces slowing down bike C. What are they?

e What will happen to bike D as it goes through the puddle? Why will thishappen?

?

knowledgeS

A

B

C

D

Anita got her mum’s wedding ring stuck on her finger. Her mum added a little washing up liquid to the ring before trying to pull it off.

2 a How can adding washing up liquid help remove the ring?

b The washing up liquid acted as

a .

c What other substances could be used instead of washing up liquid? Give two examples.

? 3 a How does the wax help Angela ski faster?

b What two forces slow her downas she travels down a ski slope?

Angela enjoys going fast on her skis. Before going on the slope, she always rubs wax on the bottom of her skis.


7Kd/7 A weight and

friction experiment

7

K

d

John and Neena set up the experiment shown in the diagram.

Method

1 They put masses on the sledge and pulled it gently with a force meter until it just started to move.

2 They recorded the force on the string needed to move thesledge.

3 Extra masses were then added to the sledge to make itheavier.

4 They recorded the force needed to move the heavier sledge.

5 They repeated this several times.

6 The results of their experiment are shown in the table.

Mass of the sledge Weight of sledge Force needed to move

and masses (kg) and masses (N) the sledge (N)

2.4 10.0

2.8 11.5

3.2 13.0

3.6 14.5

4.4 17.5

1 Copy the table and fill in the middle column. Remember that 1 kg has aweight of 10 N.

2 What is the name of the force acting between the sledge and the table?

3 Plot a graph of the results on graph paper. Put the weight of the sledge andmasses on the horizontal axis, and the force needed to move the sledge onthe vertical axis.

4 From your graph, find out the force needed to move the sledge when ithas a weight of 40 N.

5 Write a conclusion to their experiment.

6 Name two substances which could help the sledge move more easily.

?

considering, presenting, observingS

0124 35679 810

sledge


7

K

e

7Ke/1 Speed check

Name Class

1 The pictures show things moving at different speeds. Write the speedsunder the pictures. The speeds you need are in the box.

?

37 km/h 240 km/h 6 km/h 8 cm/minute 750 km/h 25 cm/year

2 A car going at 30 mph covers 30 miles in each hour. Write out in words whatthe following figures mean:

a 60 mph

b 20 km/h

c 40 m/s

3 Look at the pictures again.

a The force that stops the racing car from skidding is called .

b Two forces are trying to make the racing car slow down. They are

and .

c Label the forces on the fighter aircraft below. Use the letters next to each phrase in the box.

A forward forcefrom the engine

B air resistance

C gravity

D upward forcefrom the wings

numeracy, revisionS


7

K

e

7Ke/2 The Highway Code

The Highway Code is a booklet that contains all the rules and recommendations forusing the roads safely. It includes details of stopping distances. The Highway Codeapplies to all things using the road, including bicycles.

numeracy, presentingS

Speed (mph) Thinking distance (m) Braking distance (m) Stopping distance (m)

20 6 6

30 9 14

40 12 24

50 15 38

60 18 55

70 21 75

1 Copy the table and complete the last column.

2 Explain what these distances are:

a thinking distance

b braking distance

c stopping distance.

3 Why do you think the Highway Code does not include stopping distances forspeeds greater than 70 mph?

4 Plot a graph to show the information in the table. Plot all three sets of distances on one graph, using different colours for each one. Make a key to show which line is which. You will need axes like this:

a Draw a line of best fit through the points for thinking distance.

b Draw a smooth curve through the points for braking distance and stopping distance.

5 Use your graph to work out these distances for a car travelling at 55 mph.

a thinking distance

b braking distance

c stopping distance.

6 How would the numbers in the table change if:

a the driver had been drinking alcohol

b the car was going uphill?

c Explain your answers.

?

speed (mph)

dis

tan

ce (

m)


7

K

e

7Ke/3 Looking back!

Name Class

1 Complete all theclues to find themystery word.

a A force whichkeeps us on theground.

b A unit of mass.

c The force thatslows downthings movingthrough water.

d This force makesan object float in water.

e The units forthis are newtons(peoplesometimes usekilograms bymistake).

?

f These surfaces have less friction than rough surfaces.

g A bit of oil reduces this.

h The amount of substance in you, gravity can’t change this.

i Objects do this in water when the upthrust is big enough.

j If there are two equal and opposite forces on something, we say theforces are __________ .

k This goes back to its original shape after being stretched, that is whyit is used in force meters.

l A scientific word used to describe oiling or greasing a machine.

m The units for force.

2 Explain what the ‘mystery word’ means.

a

b

c

d

e

f

g

h

i

j

k

l

m

literacy, revisionS


7Ke/4 Bungee jumping

Name Class

numeracyS

519

7

K

e

Rebecca did a bungee jump. The graph below shows her height during the first 10seconds of her jump. The statements underneath the graph describe what happened.

Read the statements carefully, and then write numbers on the graph to which part ofthe graph each statement is describing. Then write an explanation on the lineunderneath each statement of why you put that statement where you did.

1 Rebecca is really scared!

2 ‘I’m going too fast!’ Rebecca screams.

3 ‘Thank heavens that’s over!’ Rebecca says.

4 Rebecca has stopped moving.

5 People on the ground can see Rebecca moving back up.

6 The ground seems really close to Rebecca.

7 ‘The bungee is starting to pull me back up!’ Rebecca wails.

Time (s)

Hei

ght

(m)


7Ke/5 Calculating speed

7

K

e

1 The car on the motorway can travel 1860 metres in 60 seconds. Work outhow fast the car is going. Don’t forget the units!

2 The dog runs 1980 metres in 5 minutes. How fast is he running?(Hint: Remember, there are 60 seconds in each minute.)

3 a How far will the girl cycle in 1 hour? (Hint: 1 hour = 3600 seconds)

b How far will the train go in 60 seconds?

c How far will the cockroach run in 10 seconds?

4 How long will it take for the girl to cycle 4 km?

5 a How many metres will the train travel in 1 hour?

b How far is this in kilometres?

?

numeracyS

speed = 8.5 m/s

speed = 0.2 m/s

speed = 56 m/s

To work out a speed you have to know a distance and a time. You can calculatethe speed using this formula:

speed =

Sometimes we know the speed of something, and we want to find out how far itwill go in a certain time, or how long it will take to get somewhere.

The formula can be arranged like this:

distance = speed ¥ time or time = distancespeed

distancetime

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