7K
Quick Quiz
On your answer sheet, circle the correct letter for each question.
7Ka
1 A force is:
A a spring.
C a movement.
3
displacement can
B an engine.
D a push or a pull.
2 Which answer shows three non-contact
forces?
A magnetism, gravity, friction
B gravity, friction, upthrust
C gravity, static electricity, magnetism
D upthrust, static electricity, friction
7
K
measuring
cylinder
You can find the volume of the object in
the can by:
A measuring the object and multiplying
the numbers.
B measuring the volume of water it
displaces.
C weighing the object.
D using a thermometer.
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.
4 The density of water is 1 g/cm3. Which of
these objects will float in water?
A density = 2 g/cm3
B weight = 2 N
C density = 0.5 g/cm3
D mass = 1 g
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 of
something.
B the volume of a fixed weight of
something.
C the weight of a fixed volume of
something.
D the mass of a fixed volume of
something.
7Kc
1 An elastic material:
A does not stretch.
B stretches and stays in its new shape.
C stretches and then goes back to its
original 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
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7K
3 Which is true?
A Your weight would be the same on the
Earth and on the Moon.
B Your mass would be the same on the
Earth and on the Moon.
C Your weight would be more on the
Moon than on the Earth.
D Your mass would be less on the Moon
than on the Earth.
4 What do most force meters have inside
them?
A a light bulb
B a spring
C wires
D a battery
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 to
stop quickly?
A a tired driver
B going uphill
C worn tyres
D a wet road
7Kd
1 Which of the following sentences about
friction is not correct?
A Friction can make an object get hotter.
B Friction wears car tyres away.
C Friction slows down a ball rolling in
grass.
D Friction can speed up a falling object.
4 This graph shows the distance moved by
someone catching a bus.
80
70
2 Which of these would produce the most
friction 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 between
them
60
Distance (m)
7
K
Quick Quiz (continued)
e
50
40
30
c
20
d
b
10
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 of
a pencil
D friction between your shoes and the
floor
f
0
a
0
2
4
6
8 Time (min)
Which part of the graph shows the person
waiting at the bus stop?
A a to b
B b to c
C c to d
D d to e
4 Which of the following is not an example
of a lubricant?
A grease for bicycle chains
B rubber on car tyres
C water on swimming pool tiles
D oil in a car engine
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Target Sheet
7K
Name
Topic
7Ka
7Kb
7Kc
7Kd
7Ke
Class
1
Targets
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.
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 object
will float.
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.
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.
1
Know what is meant by speed, and
know the units for speed.
2
Know how the stopping distance of
a car depends on speed.
3
Know some of the factors that affect
the stopping distance of a car.
4
Know how to interpret simple
distance / time graphs.
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I have learned this I have revised this
7
K
477
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Word Sheets
7K
Word sheets that include new words from the ‘Focus on:’ pages are available on the
Exploring Science website.
7Ka – The forces are with us
Word
7
K
Pronunciation
Meaning
air resistance
A force that tries to slow things down that are moving through air. It is a type of
friction.
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 of
friction.
7Kb – That floating feeling
Word
Pronunciation
Meaning
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.
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7K
Word Sheets (continued)
7Kc – Balancing act/Hooked!/Weighing in
Word
Pronunciation
Meaning
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 stretched
or 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 a
large 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 is
measured in newtons (N).
7Kd – Friction
Word
Pronunciation
Meaning
air resistance
A force that tries to slow things down that are moving through the air. It is a type of
friction.
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 of
friction.
7Ke – The need for speed
Word
Pronunciation
Meaning
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
hour (km/h)
Units for speed when the distance is measured in kilometres and the time is measured
in hours.
metres per
second (m/s)
Units for speed when the distance is measured in metres and the time is measured
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 the
thinking distance and the braking distance added together.
thinking distance
The distance a car travels while the driver is deciding to press the brake pedal.
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7
K
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
7
K
colour
flavour
or
shape
.
b Forces can change the
direction
pull
push
speed
,
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
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. There
are no horizontal forces on it.
Draw and label two forces
acting on the boat.
[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]
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7
K
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?
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.
5
4
Distance (miles)
7
K
3
2
1
0
0
10
20
30
40
Time (minutes)
50
60
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 and their effects
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.
7
K
The units for measuring force are newtons (N).
Friction is a force caused by two things rubbing together. Air resistance and water
resistance are kinds of friction. They are sometimes called drag.
Upthrust pushes things up. Solid things, like your chair, give you upthrust. Things
float in water because of upthrust.
Contact forces need to touch the thing that they are affecting. Examples of contact
forces are:
●
●
●
●
friction
air resistance
water resistance
upthrust.
Some forces do not need to touch the thing that they are affecting. They are called
non-contact forces. There are three non-contact forces:
●
●
●
magnetism
gravity
static electricity.
Balanced forces
upthrust
downward force
from 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 will
the wall!
A rocket in space does not need to use its engine to keep moving. There is no air in
space, so there is no air resistance to slow it down.
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7K
Summary Sheets (continued)
If you are floating in a swimming pool, your weight and the upthrust are balanced.
upthrust
7
K
weight (gravity)
Density and floating
You can decide if something will float by working out its density. Density is the mass
of a certain volume of something, and it can be calculated using this formula:
density =
mass
volume
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 forces
Elastic materials will stretch with a force and then return
to their original shape when the force is taken away.
N
0
1
Materials like Plasticine will stretch with a force but they
will not return to their original shape afterwards.
Plasticine is not elastic.
Springs are used to measure the size of a force because
they are elastic. A big force stretches a spring further than
a small force. Force meters have springs inside them.
2
3
4
5
This force meter
is measuring a
force of 1 N.
Weight and mass
Your mass is the amount of substance in your body. Your mass is measured in
kilograms (kg).
Your weight is a force caused by gravity pulling on your body. The newton (N) is the
scientific 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 the
force 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.
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Mark schemes
7K
Matching End of Unit Test marks to NC levels
Quick Quiz
Question
7
K
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
Level
Marks
available
Cumulative
total
Suggested
threshold to
achieve 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
End of Unit Test
Question
Level
Answers
Mark scheme
1
2
3
a Push, pull
b Shape, speed, direction
1 mark – answers either way round
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 mark
tyres on road)
b any example of friction not being useful (e.g. in an 1 mark
engine, axles)
4
3
4
4
5
a Increase roughness of surface or use high friction
material (e.g. rubber)
b Make surfaces smoother;
use a lubricant
1 mark
1 mark
1 mark – accept ‘use oil’ or similar answer
4
5
5
5
5
6
a C
b Slow down
c Speed up
d Water resistance
e No friction in space to slow it down, so speed
will stay the same
1 mark
1 mark – accept equivalent answers
1 mark – accept equivalent answers
1 mark
1 mark – mark for each point or any sensible equivalent
5
5
5
Equal sized up and down arrows drawn
Upthrust and gravity (or weight) correctly labelled
1 mark
1 mark
6
5
Newtons
1 mark
7
6
7
A ticked
C ticked
1 mark – no marks if B also ticked
1 mark – no marks if D also ticked; remove one mark if E ticked
8
7
7
6
a g/cm3
b Mass ∏ volume
c Numbers substituted correctly and correct answer
(0.5 g/cm3)
1 mark
1 mark if both correct
1 mark – mark for substitution, mark for correct answer
9
5
7
a 4.5 miles
b Section of graph between 50 and
54 minutes labelled
c 6 minutes
1 mark – mark if no units or incorrect units
1 mark
6
240
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Teacher’s Guide 7
1 mark
© Pearson Education 2002
7K
Summary Sheets (continued)
Friction
Friction is a contact force. Friction can:
●
●
●
●
slow things down
wear things away
produce heat
make a noise.
Friction is sometimes helpful, for instance:
●
●
●
7
K
Friction is not always helpful:
your shoes grip the floor because
of friction
tyres and brakes use friction
pencils write because of friction.
●
●
parts of engines wear away because
of friction
friction makes bicycles harder
to pedal.
Friction can be increased by using rough surfaces, or by using materials like rubber
that have a lot of friction.
Friction can be reduced by using smooth surfaces, or by lubrication. Things like oil or
grease are lubricants, and help things to move past each other easily.
Speed
To measure how fast something is travelling you need to measure the distance it
travels 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 distances
A moving car takes some time to stop. The distance it travels while the driver is
deciding whether to stop is called the thinking distance, and the distance it travels
while it is slowing down is called the braking distance. If you add the two distances
together 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.
3
A journey can be shown
on a distance/time graph.
This graph shows a person
running, then stopping for
a rest, then walking
slowly. The steeper the
line on the graph, the
faster they are moving.
Distance (km)
Distance/time graphs
2
1
0
0
10
20
30
40
Time (minutes)
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7Ka/1
Forces in action
Name
P
7
K
a
Class
Fill in the gaps on this sheet. The words you need are given in the brackets.
1
Apparatus
●
2 magnets
(attracting/repelling) each other.
The magnets are
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
Apparatus
●
wood
●
ice cube
wooden block
ice
The force of
(friction/gravity/magnetism) tries to stop
the blocks moving across the desk.
It is
the ice is
(easier/harder) to push the block of ice, because
(smoother/rougher).
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7Ka/1
P
Forces in action (continued)
3
Apparatus
●
●
It is
The plastic string has a
there is less
natural string
plastic string
(harder/easier) to tie a knot in the plastic string.
(rough/smooth) surface so
(friction/gravity/magnetism).
4
Apparatus
●
The force from the spring gets
stretched further. The spring is
spring
(bigger/smaller) if it is
(pulling/pushing).
5
Apparatus
●
0
1
●
2
3
force meter
object
4
5
Weigh the object.
How much does your object weigh?
The force of
object downwards.
(friction/gravity/magnetism) is pulling the
6
Apparatus
●
(less time/more time) to fall if it is
(more/less) when
The paper takes
crumpled up. The air resistance is
the paper is crumpled up.
S
observing
Exploring Science for QCA
Two sheets of
paper
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7
K
a
7Ka/2
Contact and
non-contact forces
Name
Class
1 Cut out the five pictures and five labels at the bottom of the page.
2 Stick the forces in the correct boxes.
7
K
a
3 Stick the correct label below each picture.
Non contact forces
Contact forces
✄
Magnetism
S
Static
electricity
Friction
Gravity
Upthrust
knowledge
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7Ka/3
Forces are
everywhere
Name
?
Class
1 Which forces are pushes and which ones are
pulls? Write the correct words in the spaces.
7
K
a
2 Look at the pictures below. Write the names of the forces next to the arrows.
A
B
C
D
E
F
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
d Three forces which can act from a distance are
and
S
being involved.
,
forces.
knowledge
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7Ka/4
Find the forces
Name
?
Class
Write the answers to the clues in the spaces.
Clues
7
K
a
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 red
and the non-contact forces in blue.
(Use pen and pencil if you do not have any coloured pencils.)
S
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
knowledge, literacy
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Which way is the
force acting?
7Ka/5
Name
?
Class
Mark the diagrams with arrows to show the forces. Most of the pictures have
more than one force. Write in the name of each force.
Think about whether the forces are balanced or not. When you draw arrows
to 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.
A
B
magnetism
C
D
E
F
G
I
H
S
knowledge
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7
K
a
Bathroom scales
7Ka/6
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 bathroom
scales. Real scales are a bit more complicated than this. They need more bits and
pieces to make sure that everything fits into a fairly small, flat case.
pointer
30 0
500
100
800
pinion
1100
120
0
lever
00
weight of
person
90
0
13
00
70 0
0
20
0
0
60
spring
400
N
10
7
K
a
400
rack
pivot
When you stand on the scales you are pushing down on a lever that is attached to the
spring. The lever and spring are arranged so that you do not make the lever move
very far – this is so everything can fit inside a small case. The end of the lever moves a
rack, which is a long piece of metal with teeth along one side. The rack is touching a
pinion, a wheel with teeth on it. The pinion is attached to a round dial which has the
weights marked on it. When the rack moves down, it turns the pinion, which turns
the dial. When you stand on a set of scales you can see the dial moving. The number
on the dial that ends up under the pointer shows your weight. Most bathroom scales
turn 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 stand
on 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 the
ones 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 be
changed 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 stand
on the bathroom scales. How could you weigh her using the scales?
S
knowledge, literacy
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7Kb/1
Floating, sinking
and density
Is there a connection between the density of an object and whether
it floats or sinks?
P
Density measures how much mass there is in 1 cm3 of something. You have to
work it out from a mass and a volume.
Apparatus
●
●
●
Different materials
Ruler
Calculator
●
●
●
Bowl
Water
Balance
Method
1 Make a table for your results, like this:
Material
Mass
Length
Height
Width
Volume
Density
Floats
(g)
(cm)
(cm)
(cm)
(cm3)
(g/cm3)
or Sinks?
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:
0
1
2
3
4
5
6
7
8
9
10
height
length
width
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.
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Floating, sinking and density
(continued)
Considering your results/conclusions
1 Look carefully at your results. Do materials with high densities float or sink?
2 Copy and complete these sentences. Choose from the words in the
brackets.
Density is a way of saying how much (mass/volume) there is in 1 cm3 of a
material. A material with a high density feels (lighter/heavier) than a
material with a low density.
7
K
b
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.
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Upthrust in
different liquids
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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 not
big enough to make them float.
You can measure upthrust by finding out how much the weight of an object
changes when you put it in water.
Apparatus
●
●
●
Force meter
String
Object
●
●
●
Different liquids
Beaker
Balance
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:
Liquid
Weight in air (N)
Weight in liquid (N)
Upthrust (N)
Density of liquid (g/cm3)
3 Carry out the experiment and fill in your table. You calculate the number in the
fourth 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 equal
volumes of each liquid and find their mass. Work out the density and write your
results 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 of
upthrust it provides?
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Floating questions 1
Name
?
Class
1 Josh was in the sea at high tide
when 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.
7
K
b
Use the words in the box to complete these
sentences. Some words can be used more than once.
gravity
upthrust
a The stone felt lighter when it was under
water
. This is because
weight
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.
3 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 with
you on it.
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Floating questions 2
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?
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 with
you on it.
3 The pictures below show objects that have just been placed below the
surface of the water. The arrows show the direction and size of the forces
affecting each object.
X
Y
Z
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 =
mass
volume
Material
Mass (g)
Volume (cm3)
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
3200
2000
Brick
Density
5 Make a list of all the materials in the table that will float.
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The Plimsoll line
This story started about two hundred years ago in the early days of the British
merchant navy. Greedy ship owners would often overload the ships with goods they
wanted to sell in far-away countries.
7
K
b
Because they were so overloaded, many
ships would sink if they met a storm at
sea. The sailors’ families had to wait for
months before they knew if the crew had
survived the trip. Many never came back –
they were ‘missing, presumed lost’.
In 1870, a member of Parliament called
Samuel Plimsoll decided that too many
ships were being lost at sea due to
overloading. He passed a law forcing ship
owners to have a special line painted on
the side of each ship. Loading of the ship
had to stop as soon as the water level
reached this line. If the water level went
above the line, the ship owners would be
fined or imprisoned.
Plimsoll Line
TF
F
T
S
Load lines
TF
F
Tropical Fresh Water
Fresh Water
Tropical Salt Water
Summer
If a ship was
loaded to here
T
in the summer,
S
the water would
W
only come up to
WNA here in the winter.
W
Winter
WNA
Winter North
Atlantic
The ‘Plimsoll line’ is still in use today and can be seen painted on the side of all cargo
ships. Ships also have load lines for different parts of the world. These are very
important for ships which travel from the cold seas of Britain to the warmer tropical
seas. Warm sea water produces slightly less upthrust than cold sea water, so ships float
lower down in warm water. Fresh water also produces less upthrust than sea water.
?
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 sea
into a fresh water river?
5 There are two reasons why tropical fresh water produces less
upthrust 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 the
water in the cup. How does this affect the way the egg floats?
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Archimedes
Archimedes lived in Syracuse, Italy, and was a great inventor and philosopher. One of
the scientific facts that he discovered is called Archimedes’ Principle. The upthrust on
something 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?
3
4
5
6
7
6
7
8
9
10
c What is the weight of the water
in the small beaker?
This volume
of liquid is the
same as the
volume of the
stone.
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.
0
1
2
3
4
a What is the weight of the
wooden block?
0
1
2
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?
3 All the beakers have water in them.
X
Y
Z
a Which object is the heaviest? How do you know?
b Write the three objects in order of their weight, starting with the
heaviest. 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 out
what an ‘Archimedes screw’ is and what it is used for.
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b
Make a force meter 1
7Kc/1
P
Apparatus
●
●
●
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K
c
Stand and 2 clamps
Metre rule
Spring
●
●
●
Mass holder and masses
G clamp
Objects to weigh
Method
1 Set up your apparatus like this:
2 Measure the position of the bottom
of the spring. You can use another
ruler to help you. Write your result
in the table.
Hang the holder on the spring and
measure the length again. The holder
has a mass of 100 g. Write your
result in the table.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
3 Put more masses on the spring and measure its length each time.
Recording your results
1 Make a copy of this table and fill it in.
Mass
Weight
Length of spring
(g)
0
100
200
300
400
500
(N)
0
1
2
3
4
5
(cm)
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Make a force meter 1 (continued)
Length of spring
(cm)
2 Plot a graph of your results on graph paper. You will need to use axes like
these:
7
K
c
0
1
2
3
Weight (N)
4
5
3 Now you can use your force meter to weigh other things. Hang an object on
the spring and measure its length. Then use your graph to find its weight,
like this:
Length of spring (cm)
This is the
length you
measured.
This tells you the
weight of the object.
Weight (N)
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P
Make a force meter 2
Apparatus
●
●
●
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c
Stand and 2 clamps
Metre rule
Spring
●
●
●
Mass holder and masses
G clamp
Objects to weigh
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.
1
2
3
4
5
6
7
Method
8
9
10
1 Set up your apparatus like this:
2 Draw a table for your results, like this:
11
12
13
14
15
16
Mass
Weight
Length
Extension
(g)
(N)
(cm)
(cm)
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 the
measurement 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 the
length of the spring minus the length for zero mass.
7 Plot a graph of weight (along the bottom) and extension (up the side).
This is the
extension you
measured.
Extension (cm)
8 Now you can use your
force meter to weigh
other things. Hang an
object on the spring and
measure its length. Work
out the extension and
then use your graph to
find its weight, like this:
This tells you the
weight of the object.
Weight (N)
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What do forces do?
Name
?
Class
1 Look at the four pictures below. The size of the arrow represents the
size of the force and its direction.
For each picture fill in the gaps.
A
This force is called
The forces
are
This force is called
B
(balanced/unbalanced).
This force is called
The forces
are
This force is called
(balanced/unbalanced).
The forces are
C
(balanced/unbalanced).
The car
(will/will not) move.
The forces are
D
(balanced/unbalanced).
The
(boy/girl)
will win the contest.
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The size of a force
Name
?
Class
1 The unit of force is called a
.
2 The pictures below show examples of forces. Write the
correct size of each force in the space below each picture.
Choose numbers from the box.
7
K
c
50 000 000 N
0.5 N
650 N
10 N
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
S
kilogram
newton
20 N
2 kg
80 kg
.
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Stretch, stretch,
stretch and …
7Kc/5
Matilda and Ravi carried out
an experiment in class which
showed how a spring was
extended (stretched) by
different forces.
7
K
c
Their results are shown in the table below.
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
They wrote this conclusion:
This experiment shows that a spring stretches by the same amount each time a 100 g force is added to
the other weights.
?
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 of
forces could you measure?
3 Ravi used his force meter to weigh some other objects. He wrote down the
extension of the spring when he hung each object on it:
Object
Extension
A
2.0 cm
B
19.0 cm
C
4.5 cm
D
6.5 cm
Work out the weight of each object using your graph.
4 Matilda and Ravi made mistakes in their conclusion. What were they?
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Climbing ropes
Rock climbers and mountaineers use ropes to stop them getting hurt if they fall, but
did you know that climbing ropes are stretchy?
7
K
c
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 the
spring depends on how far it has been stretched.
The same thing happens with climbing ropes.
A
?
B
C
D
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 change
the speed of something that is moving.
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?
Climbing ropes (continued)
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 or
not 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 rope
increases 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.
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Materials and
friction 1
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Name
Class
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
7
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and the slide must be as
P
(big/small) as possible.
Apparatus
●
●
●
Squares of different types of materials
Wooden block with a hook
4 drawing pins
●
●
Force meter
Large mass (about 500 g)
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.
0
1
2
3
4
5
6
7
8
9
10
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 the
mean force needed.
6 Repeat steps 1 to 5 for other materials.
Recording your results
Material
Force needed to pull block (N)
1st pull
2nd pull
3rd pull
Mean force
(N)
Find the
mean by
adding up
all three
results, then
divide your
answer
by 3.
Show your results in a bar chart.
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Materials and friction 1 (continued)
Considering your results/conclusions
It took the biggest force to pull the block with
This material has the
on it.
(most/least) friction.
on it.
It took the smallest force to pull the block with
This material has the
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(most/least) friction.
If I wanted to go fast down a slide, I would wear clothes made
from
S
.
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Materials and
friction 2
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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.
7
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P
Apparatus
●
●
●
Squares of different types of materials
Wooden block with a hook
4 drawing pins
●
●
Force meter
Large mass (about 500 g)
0
1
2
3
4
5
6
7
8
9
10
Planning
2 Describe how you would carry out an experiment to find out which material
would be best for wearing on a slide. Remember to explain how you will make
sure your investigation is fair.
Recording your results
3 To get more accurate results, you should test each material three times and find
the mean force. Your table of results should look like this:
Material
Force needed to pull block (N)
1st pull
2nd pull
3rd pull
Mean force
(N)
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/conclusions
6 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.
Evaluation
7 Is there any way that you could have improved your investigation?
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Friction – true
or false?
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The statements below are all about friction. Some are true, some are false, and some
are partly true.
1 Cut out the statements. Work in a group to sort them into three piles, and make
sure 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 of
when friction is not useful.
True
S
False
Partly true
Friction always slows things down.
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 of
friction.
You could not pick up a cup of tea
without friction.
You could drink from a glass without
friction.
Snow increases the friction between
your shoes and the ground.
Friction is useful in playgrounds.
Pencils do not need friction to write.
There is no friction when you are roller
skating.
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Friction around us
Name
?
Class
1 Copy the sentences and fill in the missing words.
The words you need are in the box.
7
K
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force
smooth
rough
surfaces
caused by two
Friction is a
moving over each other.
friction than
surfaces produce more
surfaces.
2 Look at these diagrams.
Put a circle around the all the
places where there is friction.
One has been done for you.
3 Look at these pictures.
sandpaper
block
lab bench
polished table
cork tile
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
S
.
(most/least) friction.
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?
What’s rubbing?
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
away things that rub against each other.
, and
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.
A
B
C
D
E
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.
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Lubrication
C
B
A
D
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?
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 this
happen?
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.
Angela enjoys going fast on her skis.
Before going on the slope, she always rubs
wax on the bottom of her skis.
?
3 a How does the wax help Angela
ski faster?
b What two forces slow her down
as she travels down a ski slope?
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A weight and
friction experiment
John and Neena set up the
experiment shown in the diagram.
sledge
Method
0
1
2
3
4
5
6
7
8
9
10
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 the
sledge.
3 Extra masses were then added to the sledge to make it
heavier.
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 a
weight 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 and
masses on the horizontal axis, and the force needed to move the sledge on
the vertical axis.
4 From your graph, find out the force needed to move the sledge when it
has a weight of 40 N.
5 Write a conclusion to their experiment.
6 Name two substances which could help the sledge move more easily.
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Speed check
Name
?
Class
1 The pictures show things moving at different speeds. Write the speeds
under the pictures. The speeds you need are in the box.
7
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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 what
the 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 force
from the engine
B air resistance
C gravity
D upward force
from the wings
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numeracy, revision
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7Ke/2
The Highway Code
The Highway Code is a booklet that contains all the rules and recommendations for
using the roads safely. It includes details of stopping distances. The Highway Code
applies to all things using the road, including bicycles.
?
Speed (mph)
Thinking distance (m)
Braking distance (m)
20
6
6
30
9
14
40
12
24
50
15
38
60
18
55
70
21
75
Stopping distance (m)
7
K
e
1 Copy the table and complete the last column.
2 Explain what these distances are:
a thinking distance
b braking distance
c stopping distance.
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.
distance (m)
3 Why do you think the Highway Code does not include stopping distances for
speeds greater than 70 mph?
speed (mph)
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.
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7Ke/3
Looking back!
Name
?
Class
1 Complete all the
clues to find the
mystery word.
7
K
e
a
A force which
keeps us on the
ground.
b
A unit of mass.
c
The force that
slows down
things moving
through water.
a
b
c
d
e
f
g
h
i
d This force makes
an object float
in water.
e
The units for
this are newtons
(people
sometimes use
kilograms by
mistake).
j
k
l
m
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 the
forces are __________ .
k This goes back to its original shape after being stretched, that is why
it 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.
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literacy, revision
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Bungee jumping
7Ke/4
Name
Class
Rebecca did a bungee jump. The graph below shows her height during the first 10
seconds of her jump. The statements underneath the graph describe what happened.
Height (m)
Read the statements carefully, and then write numbers on the graph to which part of
the graph each statement is describing. Then write an explanation on the line
underneath each statement of why you put that statement where you did.
Time (s)
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.
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7
K
e
7Ke/5
?
Calculating speed
To work out a speed you have to know a distance and a time. You can calculate
the speed using this formula:
speed = distance
time
Sometimes we know the speed of something, and we want to find out how far it
will go in a certain time, or how long it will take to get somewhere.
7
K
e
The formula can be arranged like this:
distance = speed ¥ time
or
time = distance
speed
speed = 8.5 m/s
speed = 0.2 m/s
speed = 56 m/s
1 The car on the motorway can travel 1860 metres in 60 seconds. Work out
how 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?
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numeracy
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