6$03/(Karen Reynecke • Lida · PDF file2.3 Wave speed 26 Exercise 3 27 ... 1.4.2...

Physical SciencesPhysics Grade 10

Textbook and Workbook

Wilma Alberts • Ronel BernardoSias Conradie • Hendry du Plessis

Santie du Plessis • Carlien Fanoy Gerda Herbst • Patricia Lees-Rolfe

Judy McDougall • Janetta NelKaren Reynecke • Lida SmithSAMPLE

Doc ScientiaPosbus 7011

Ansfrere 1711

www.docscientia.co.za

For any queries and feedback: [email protected]

Jacques Fanoy or Stephan FanoyOffice: 011 472 8728

Fax: 086 546 1423

ISBN: 978-1-920537-12-8

First edition December 2009Second edition December 2010

Third edition December 2011Revised edition December 2012; 2013; 2014; 2015

Graphic design: Helene Jonck

All rights reserved. No part of this publication may be reproduced in any form or by any means –

mechanical or electronic, including recordings or tape recordings and photocopying – without the prior permission of the publisher.SAMPLE

INDEXUnit Page

KNOWLEDGE AREA WAVES, SOUND AND LIGHT 11

Unit 1 TRANSVERSE PULSES 11

1.1 Pulses 11

Practical activity 1 13

Exercise 1 14

1.2 Interference 15


Exercise 2 19

Summary of Unit 1 20

Mind maps of Unit 1 21

Unit 2 TRANSVERSE WAVES 23

2.1 Transverse waves 23

2.2 Interference 25

2.3 Wave speed 26

Exercise 3 27



Unit 3 LONGITUDINAL WAVES 37

3.1 Longitudinal waves in a spring 37

Practical demonstration 37

3.2 Representation of longitudinal waves 39

Exercise 4 42



Unit 4 SOUND 47



Exercise 5 50

4.1 Reflection 52

4.2 Pitch 52


4.3 Loudness 54

4.4 Quality 55


Exercise 6 57

4.5 Ultrasound 60

Exercise 7 61



Unit 5 ELECTROMAGNETIC WAVES 65

5.1 Wave/particle properties of EM radiation 65

5.2 The nature of EM waves 65

5.3 The electromagnetic spectrum 66

5.4 Properties of electromagnetic waves 67

5.5 Penetrating ability 67

5.6 Disadvantages of EM radiation 68

5.7 Particle nature of EM waves 69

5.8 Inherent sense of danger 70

Exercise 8 71



SAMPLE

Question paper 77

KNOWLEDGE AREA ELECTRICITY AND MAGNETISM 87

Unit 1 MAGNETISM 87

1.1 Magnetic poles 88

1.2 Magnets exert forces on each other 88

1.3 Magnetic and non-magnetic materials 88

1.4 Magnetic fields 89

1.4.1 Direction of a magnetic field 90


1.4.2 Magnetic field around a bar magnet 92

1.5 Theory of magnetism 92

1.6 Electromagnets and permanent magnets 93

1.7 The earth’s magnetic field 94

1.7.1 Importance of the earth’s magnetic field 95

1.7.2 Solar winds 95

1.7.3 Polar auroras 95

1.7.4 Magnetic (geomagnetic) storms 95

1.7.5 Migration of animals 95

Exercise 9 96



Unit 2 ELECTROSTATICS 101

2.1 Charges 101


2.2 Distribution of charge 103

2.2.1 Friction 103

2.2.2 Contact 103

2.2.3 Induction 104


2.3 Conservation of charge 106

2.4 Conductors and insulators 107

Exercise 10 108



Unit 3 ELECTRICAL CIRCUITS 113

3.1 Circuits 113

Activity 1 114

3.2 Potential difference 116

Practical demonstration 120

Exercise 11 121

3.3 Current strength 123

Experiment 1 125

Experiment 2 126

Exercise 12 128

3.4 Resistance 129

3.5 Ohm’s law 130

Exercise 13 134



Question paper 143

KNOWLEDGE AREA MECHANICS 151

Unit 1 SCALARS AND VECTORS 151

SAMPLE

1.1 Introduction 151

1.1.1 Physical units 151

1.1.2 Direction of a vector 153

1.1.3 Graphical representation 154

1.1.4 Representation of a vector 155

1.1.5 Net or resultant vector 155

1.1.6 Addition of vectors 155

Exercise 14 157


Unit 2 MOTION IN ONE DIMENSION 161

2.1 Position 161

2.2 Movement in one dimension 163

2.3 Distance and displacement 164


Exercise 15 168

2.4 Speed 169

2.5 Velocity 171

Exercise 16 175

2.6 Acceleration 177

Experiment 3 187

Exercise 17 189



Unit 3 DESCRIBING MOVEMENT 197

3.1 Instantaneous speed and instantaneous velocity 197

3.2 Graphs of motion 198

3.2.1 Constant velocity 199

Activity 2 201

3.2.2 Constant positive acceleration 202

Activity 3 206

3.2.3 Constant negative acceleration 207

Activity 4 209

Activity 5 210

3.2.4 Distance-time and speed-time graphs 214

Activity 5 219

Exercise 18 221

3.3 Equations of motion 229

Exercise 19 236



Unit 4 ENERGY 245

4.1 Gravitational potential energy 245

4.2 Kinetic energy 247

Exercise 20 248

4.3 Mechanical energy and the law of conservation of mechanical energy 249


Exercise 21 257



Question paper 261

Information sheets 270

Work cited 271

SAMPLE

Doc Scientia PHYSICS textbook and workbook - Grade 10 47

KNOWLEDGE AREA: WAVES, SOUND AND LIGHT

Sound wavesSound is so much part of our lives that we just accept its presence. We do not think about how sounds are produced or how they reach our ears.

Practical activity 3 Date: Aim: To investigate how sound is produced.

Apparatus: A vuvuzela

Method:

1. Put your hand on a vuvuzela. Do you feel any vibrations? _________________________________________

2. Now while your hand is on the vuvuzela, blow into the vuvuzela. What do you feel?

_________________________________________

_________________________________________

_________________________________________

Conclusions:What conclusions can you draw from this practical activity?

__________________________________________________________________________________

__________________________________________________________________________________

UNIT 4 SOUND

Pitch

SoundLoudness

Quality

Ultrasound

SAMPLE

waves, sound and light

48 Doc Scientia PHYSICS textbook and workbook - Grade 10

Discussion about the practical activityEnergy from a vibrating object is transferred to its particles inside.• The air that you blow causes energy to be transferred to the air molecules in the vuvuzela, which

then causes the vuvuzela to vibrate and a sound is produced.

Sound is propagated by vibrations and therefore needs a medium. To explain how sound is propagated in air, we are going to use the example of a loudspeaker.

The diaphragm (or cone) of a loudspeaker vibrates (in and out) causing the surrounding air molecules to be compressed and then stretched apart.

The air particles vibrate with the same frequency as the loudspeaker.

This vibration causes a regular alternating change in the air pressure.

Practical activity 4 Date:Aim: To demonstrate that sound needs a material medium.

Apparatus:• Two 340 mℓ cool drink cans• Two nails• String or thin copper wire

Method:1. Pierce a hole in the bottom of each can. 2. Push the string through the hole of one of the cans and then attach it to the nail so that the nail is

inside the can and stops the string from coming loose. 3. Do the same with the other end of the string and the other can.4. You and a friend (each holding a can) must walk away from each other until the string is taut.5. Talk to each other using the cans as a telephone. (The person talking puts their mouth over the

opening of one of the cans and the person listening puts the other can over their ear.)

Questions:1. Can you hear your friend talking if they talk softly without using the cans? ___________________________________________________________________________

2. Can you hear your friend talking if they talk softly using the cans?

___________________________________________________________________________

3. What conclusions can you draw?

___________________________________________________________________________

SAMPLE



It is not possible to see these longitudinal waves. An oscilloscope is used to convert the information of a longitudinal wave into a graph that looks like that of a transverse wave. Longitudinal waves hit the microphone, which is attached to an oscilloscope. When a compression reaches the sensor in the microphone, the greater pressure is converted into an electrical pulse and it is seen as a crest. If there is a rarefaction (low pressure), the sensor registers a negative pulse and the information is shown on the screen as a trough.

These compressions and rarefactions – a longitudinal wave – move towards a person’s ear, where the sound can be heard. The number of vibrations per second is the frequency of the wave.

movement of slinky

direction of wave propagation

λ

compression compressionrarefaction

table

loudspeakermovement of air particles

direction of wave propagation

compression compression

rarefaction

loudspeaker

compressions rarefaction

direction of wave movement

direction of travelling wave

compression

rarefaction

oscilloscope

air

pres

sureSAMPLE



Sound waves are pressure waves, and therefore the type of medium determines the speed with which the waves move. Two factors that determine the speed of a wave: • elasticity of the medium. • density of the medium.

The elasticity can be described as how stiff the medium is (how quickly the particles return to their original position). The speed of sound is faster if the elasticity is greater.Sound moves faster through steel (particles return to their original position quickly) than through rubber which is less stiff (particles take longer to return to their original position).Sound also moves faster in solids than in liquids or gases, which are less elastic.

The speed of sound is faster if the density of the medium decreases, but the elasticity remains constant.

Sound travels faster in hot air (low density) than in cold air (higher density). The same is true for hot and cold water.

Exercise 5 Date: 1 A sound wave with a frequency of 550 Hz moves through a 20 m long steel rod. The speed of sound in steel is 6 000 m·s-1.1.1 Calculate how long the wave takes to move through the rod.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

1.2 Calculate the period of the wave. 1.3 Calculate the wavelength of the wave.

______________________________ ______________________________

______________________________ ______________________________

______________________________ ______________________________

Quick factsSound cannot be heard in space, as there is no material medium in which the waves can travel.

SAMPLE



2.1 A tuning fork vibrates 4 096 times in 8 seconds. Calculate the frequency of the vibration.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

2.2 Calculate the period of the vibration. 2.3 Calculate the wavelength of the sound that is produced. (The speed of sound in air = 340 m·s-1.)

______________________________ ____________________________________

______________________________ ____________________________________

______________________________ ____________________________________

2.4 The speed of sound in water is 1 500 m·s-1. Calculate the wavelength of the same sound in water.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

2.5 Draw a conclusion about the wavelength of the sound as the medium changes. Give a possible reason for this.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

2.6 What is the elasticity of a medium? _____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

2.7 Will sound move faster in cold or hot water?

_____________________________________________________________________________SAMPLE



Practical activity 5 Date:Aim: To investigate the pitch of a note.

Apparatus: • A ruler• A table

4.1 Reflection

The reflection of sound is probably the most well-known property of sound. When you talk in a furnished room, part of the sound is absorbed by the carpets, furniture, curtains and wall hangings. If the room was empty, you would soon be aware of the reflection of sound. We call this reflection an echo.

When the sound is reflected off a surface far away, it is heard as a separate sound.

When a sound is reflected by an object, the echo is always softer, since part of the energy has been absorbed by the reflecting object.

4.2 Pitch

The pitch of a note indicates how high or low the note sounds.

ExamplesHow can we determine the depth of a shipwreck? A boat transmits a sound wave, and 5 s later it registers its reflection. Calculate the depth of the shipwreck, if the speed of sound in sea water is 1 480 m·s-1.

D Data v = Δt Δt = 5 s 1 480 = D ÷ 5 v = 1 480 m·s-1

Therefore: D = 7 400 m Depth of shipwreck = 7 400 2 = 3 700 m

Remember The sound went towards the wreck and was then reflected.

SAMPLE



What we learned from this practicalA lower frequency (longer wavelength) gives a lower note, e.g. when Bobby van Jaarsveld sings.

A higher frequency (shorter wavelength) gives a higher note, e.g. when Miriam Makeba sings.

Method:• Place a 30 cm long ruler on the edge of a table so that about 12 cm

of it is on the table and the rest of the ruler is over the edge of the table.

• Hold the first 2 cm on the table with your fingers and bend the section which is over the side downwards.

• Release the bent section and allow it to flick up and start vibrating. Take note of the pitch of the sound.

• Now move the ruler back so that a smaller section is over the edge of the table. Repeat the previous step.

Questions:1. What happens to the frequency of the vibrations as you shorten the

length of the ruler over the edge?

_____________________________________________________________________________

2. What happens to the pitch of the sound as you shorten the length of the ruler over the edge?

_____________________________________________________________________________

3. What can you conclude about the relationship between the frequency and the pitch of these vibrations?

_____________________________________________________________________________

compression

rarefaction

high frequency (high note)

timeair pressure

compression

rarefaction

low frequency (low note)

timeair pressure

SAMPLE



Now you can understand the difference between a woman's voice and a man's voice. Even if they speak with the same volume, a man has a lower frequency than a woman.

Loudness• The louder the sound, the greater the amount (degree) of compression. • The louder the sound, the greater the rarefaction of the medium (the amplitude).• The loudness of sound is measured in decibels (dB).• The frequency of the wave remains the same, that is, the pitch remains the same, if the amplitude

increases, but the frequency of the wave does not change.• The wavelength of the wave also remains the same if the amplitude is changed.

Interesting facts:This principle is used in instruments like a saxophone in which a “damper” is used to decrease the amplitude of the wave produced.

4.3 Loudness (volume)

A sound wave is a series of consecutive compressions and rarefactions in a medium.

To produce a louder note, the amount that the particles are compressed and rarified must be greater in order to produce a wave with greater amplitude.

It will look like this on the screen of an oscilloscope:loud sound soft sound

compression

compression

rarefaction

rarefaction

A A

time time

air

pres

sure

air

pres

sure

Quick facts:The amplitude of a wave is proportional to the energy of the wave; therefore the amplitude will decrease when the energy decreases.

SAMPLE



Practical activity 6 Date:Aim: To compare the sounds produced by a recorder (or flute) and a vuvuzela.

Apparatus: • Vuvuzela• Recorder (or flute) • Tuning fork

Method:1. Blow through the vuvuzela and then through the recorder.2. Hit the tuning fork against a table.3. Observe the different sounds.4. If you have an oscilloscope, use it to observe the wave forms of these sounds.

Questions:

1. If you have an oscilloscope, draw a sketch of the wave pattern of the vibrating tuning fork.

2. How does the sound from the vuvuzela compare to that from the recorder? ______________________________________________________________________________

3. Which of the two instruments gives a more pure note?

______________________________________________________________________________

If an oscilloscope is available:

4. How do the wave patterns that you see on the oscilloscope produced by the recorder compare to that produced by the vuvuzela?

______________________________________________________________________________

______________________________________________________________________________

The loudness of a sound does not only depend on the amplitude of a wave.

The sensitivity of a person’s ear also plays a part. For one person, a sound may be too loud, whereas for another it is perfectly acceptable.

4.4 Quality

SAMPLE



5. You blow on the recorder, first softly and then harder. What changes do you observe in the pattern on the oscilloscope? ______________________________________________________________________________

______________________________________________________________________________

The oscilloscope represents the longitudinal waves as transverse waves on the screen.The recorder produces pure notes that can harmonise with each other. The vuvuzela produces sounds that are less clear and musically less pure.

A pure sound gives a regular pattern, e.g. sound from a tuning fork.

A pure note with a regular pattern is produced by a recorder.

An impure sound gives an irregular pattern, e.g. a sound from a vuvuzela.

A note produced by a tuning fork is a pure note, as it consists of only a single frequency.

The quality of sounds produced by different instruments, differs. This depends on the number of notes that harmonise to produce that sound.

The wave pattern on an oscilloscope shows that the amplitude of a soft sound from a recorder is smaller than the amplitude from a loud note.SAMPLE



Exercise 6 Date: 1. What is meant by the pitch of a note?

______________________________________________________________________________

______________________________________________________________________________

2. The pitch of a note is dependent on the _________________ of the sound wave.

3. The loudness of a note is dependent on the ___________________ of the sound wave.

4 A note is played on the piano. The frequency of the note is 316 Hz and the amplitude is 6 cm.4.1 What is meant by a “frequency of 316 Hz”?

______________________________________________________________________________

______________________________________________________________________________

4.2 What is meant by an “amplitude of 6 cm”?

______________________________________________________________________________

______________________________________________________________________________

4.3 If a note is played, and then the same note is played again, but louder, will the: 4.3.1 frequency of the note increase, decrease or remain the same? Give a reason for your answer.

_______________________________________________________________________

_______________________________________________________________________

4.3.2 amplitude of the note increase, decrease or remain the same? Give a reason for your answer.

_______________________________________________________________________

_______________________________________________________________________

4.4 If a note is played, and then a higher note is played at the same volume, will the: 4.4.1 frequency of the note increase, decrease or remain the same? Give a reason for your answer.

_______________________________________________________________________

_______________________________________________________________________ 4.4.2 amplitude of the note increase, decrease or remain the same? Give a reason for your answer.

_______________________________________________________________________

_______________________________________________________________________SAMPLE



5 The following sound wave, produced by a tuning fork, is observed on an oscilloscope.

A few more notes are played on tuning forks. The following wave patterns are observed.

A B

C

5.1 Which one of these patterns represents a louder and higher note than the original note? Give a reason for your answer.

______________________________________________________________________________

______________________________________________________________________________

5.2 Which one of these patterns represents a higher note with the same volume as the original note? Give a reason for your answer.

______________________________________________________________________________

______________________________________________________________________________

5.3 Which one of these patterns represents a softer and higher note than the original note? Give a reason for your answer.

______________________________________________________________________________

______________________________________________________________________________SAMPLE



6 Study the following wave patterns of sound.

What is the difference (in terms of frequency, pitch, amplitude and volume) between the following notes?

Frequency Pitch Amplitude Volume

6.1 A and B

6.2 B and C

6.3 A and C

6.4 B and D

6.5 C and E

6.6 D and E

7.1 On a rainy day the speed of propagation of sound is 350 m·s-1. You see a flash of lightning and 3 s later you hear the roar of thunder. Calculate how far away you are from the lightning flash.

_____________________________________________________________________________

_____________________________________________________________________________ _____________________________________________________________________________

7.2 What is the wavelength of that flash of lightning if it has a frequency of 33 Hz?

_____________________________________________________________________________

_____________________________________________________________________________ _____________________________________________________________________________

A

C

E

D

B

SAMPLE



Ships also use ultrasound. A transmitter sends a sound wave into the water. The sound wave reflects off the bottom of the sea and returns to a receiver. The time taken for this to happen is measured. In this way, the depth of the sea can be calculated. Ultrasound used in this way is known as sonar. Sonar is also used on dive boats to see where wrecks are and to track the movement of schools of fish.

8. Explain why an echo is always softer than the original sound.

______________________________________________________________________________

______________________________________________________________________________ ______________________________________________________________________________

9. A boy is a certain distance from a large building. If he shouts he can hear the echo after 3 s. The speed of sound is 340 m·s-1. Calculate how far the boy is from the building. ______________________________________________________________________________

______________________________________________________________________________ ______________________________________________________________________________

4.5 Ultrasound

People’s sense of hearing is sensitive to sounds between 20 Hz and 20 000 Hz. Sounds above 20 000 Hz (and up to 100 000 Hz) are known as ultrasound. Although people cannot hear ultrasound, it occurs often in nature. Dolphins and bats hunt their prey using ultrasound.

receiver

sender

Quick factsAn object must be much bigger than the wavelength of a sound wave for the wave to reflect off that object. Therefore bats send out notes with a high frequency and a short wavelength.

Quick factsUltra means “higher than”.

SAMPLE



In the medical world, the use of ultrasound is extremely important.Machines that use ultrasound have replaced those that use dangerous x-rays, in many situations. When ultrasound waves are sent through tissue, the waves are partially reflected, partially transmitted and partially absorbed at the interface between tissues of different density, e.g. between bone and muscle or between muscle and fat. The reflected waves are picked up by a receiver, which then sends them to a computer, which converts them into an image. • Pregnancy:

The most well-known use is surely the sonar of a foetus. It is used to check the location and size of the foetus as well as whether the organs are developing correctly. They can also see whether there is more than one foetus.

an ultrasound image of a foetus• Treatment:

Ultrasound is used in the treatment of many conditions, one of which is kidney stones. The kidney stones are broken up with ultrasound so that the patient can pass them and not have to undergo an operation.

• Diagnosis: Ultrasound can also be used for safe and quick diagnosis, for example to see how fast a person’s blood is flowing in arteries and veins. This helps to determine if there is a blockage which needs to be fixed before it causes too much damage.

Exercise 7 Date: 1 Define: 1.1 longitudinal wave

_____________________________________________________________________________

_____________________________________________________________________________

Quick factsSonar: (SOund Navigation And Ranging)

SAMPLE



1.2 wavelength

_____________________________________________________________________________

_____________________________________________________________________________ 1.3 ultrasound

_____________________________________________________________________________

_____________________________________________________________________________

2. What is the normal range of frequencies that a human can hear?

_____________________________________________________________________________

3 You are lying on your side in an Olympic swimming pool with one ear above the surface. A friend of yours, 50 m away in the water, slaps the surface of the water with his hand. The temperature outside is 20°C and the speed of sound in air is 344 m·s-1. The temperature of the water is 15°C and the speed of sound in water is 1 480 m·s-1. Calculate:3.1 how long it will take to hear the slap with the ear that is above the water.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

3.2 how long it will take to hear the slap with the ear that is below the water. (The speed of sound in the water is 1 480 m·s-1.)

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

3.3 What conclusion can be drawn from your answers to Questions 3.1 and 3.2? Give a reason for your answer.

_____________________________________________________________________________

4. A fishing boat near the Antarctic is following a school of fish with the aid of ultrasound. A pulse is sent from the hull of the boat and one second later an echo is received from the school of fish. If the speed of sound in cold seawater is 1 490 m·s-1 is, calculate how deep the school of fish is.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________SAMPLE

SOUND WAVES

Pitch

Volume

Quality

Noise

Pure note/music note

Pure note

UltrasoundSounds above 20 000 HzUses

SAMPLE

6$03/(Karen Reynecke • Lida · PDF file2.3 Wave speed 26 Exercise 3 27 ... 1.4.2...

Documents

Transcript of 6$03/(Karen Reynecke • Lida · PDF file2.3 Wave speed 26 Exercise 3 27 ... 1.4.2...