Fundamentals of Physics

544 Pages·1975·47.82 MB·English

by  B. M. Yavorsky, A. A. Pinsky

This texlbook explains the con­
cepts and 111osL important advances
of moder physics without resort
to higher rnatl!matics. Avoids the
Lraditio11al division between clas­
sical and modern physics and en­
deavours to present all material so
as to develop quantum mechanical
concepts.
The tex lbook is i1 1tended for secon­
dary schools and as a teaching aid for
physics Leachers in general and
tech11ical secondary schools. Will
be 1'011 nd useful by correspondence
stndents studying •A' level and
first year physics,
Waves. Quantum Physics of Atoms,
ticles.
Contents. Vol. I I . Vibrations and
Molecules and Solids. Physics of
the Nucleus and Elementary Par­
Prof. BOH IS YA VOHSK Y, l>ocLor
of Physical and Mnl.horaticuJ Sci­
ences, ii in thu dupurl.111u11t of
theoret.icul phy1ic1 ut the Louin
State Pedagogicui I nstit11 te i 11 Mm1-
cow. I le has boe11 lect11ri11g i 11 higher
ed11catio1111l irLit11tio111 of the So­
viet Unin Jr tho last �f years.
Prof. Yavorsky has written about
:mo publishecl works: hooki and ar­
ticles in v ario1s scion ti tic jo11r als
1111d collected papers, anwng thorn the·
Complete Course in Physics (in three
volumes) anct' some other text-·
books and aicls for institute tea­
chers.
Assoc. Prof. AH KADY PINSKY,
Candidate of Pedagogical Sciences,
is a senior :cicntist at the Scientifie
Research Institute for Teaching
Practice of the USSH Academy of
Pedagogical Sciences. lie has spe­
cialized in the methods of physics
teaching at school and university
levels. In this field he has published
over 50 works, including several
books·. on methods of teaching
physics.
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B. M. YAVORSKY and A. A. PINSKY
FUNDAMENTALS of PHYSICS
VOLUME
I
MOTION AND FORCES.
CONSERVATION LAWS.
MOLECULAR-KINETIC THEORY OF GASES.
MOLECULAR FORCES AND STATES
OF AGGREGATION OF MATTER.
ELECTRODYNAMICS.
Translated from the Russian
by
NICHOLAS WEINSTEIN
MIR PIIBLSHEBS MOSCOW
First published 1975
Revised from the 1974 Russian edi tion
Ha anz1uuc1w. JJbllU
© lalaTeJbCTBO «HayKa», 1974
© English translation , Mir Publi shers, 1975
CONTENTS
FOREWORD 15
Part one
MOTION AND FORCES
Chapter 1 VELOCITY . . . . . . .
1 . 1 . Mechanical motion
1 .2 . Frames of reference. Paths . . 20
1 .4 . Uniform motion . . . . . . . . . .
24
1 . 6 . Average velocity . . . . . . . . . . . . 25
27
1 . 7 . Instantaneous velocity of variable motion
Chapter 2 INERTIA . . . . . . . 28
2 . 1 . The principle of inertia 28
2 . 2 . Inertial reference frames 3
2 .3 . The principle of relativity 32
35
2 .4 . Galilean transformations . . . . . . 33
2 .5 . Classical law of the addition of velocities
35
Chapter 3 SCALARS AND VECTORS. VELOCITY VECTOR
3 . 1 . Scalar quantities . . . . . . . . . .
3 . 2 . Vector quantities . . . . . . . . . . 36
3 .3 . Certain operations on vectors . . . . .
3 .4 . Resolving a vector into two components
3 . 5 . Velocity is a vector 40
3 .6 . Addition of velocities 42
Chapter 4 ACCELERATION 43
4 . 1 . Average and instantaneous acceleration
4 .2 . Rectilinear variable motion . . . . . 4
4 .3 . Uniformly accelerated rectilinear motion . . 44
4 .4 . Velocity graph for uniformly accelerated motion
4 .5 . Graphical calculation of displacement . . . . . . . . . 45
4 .6 . Displacemen and average velocity in uniformly accelera-
48
ted motion . · . . . . . . . . . . . . . . . . . . . .
4 . 7 . Uniform circular motion of a particle . . . . . . . . . .
4 .8 . Acceleration in uniform circular motion of a particle . . .
19
19
1 . 3 . Rectilinear motion. Motion equations
22
23
1 . 5 . Variable motion . . . . . . . . . . .
35
37
39
43
45
46
48
6 CONTENTS
Chapter 5 FORCE . . . . . . . . . . . . . . . 50
5 . 1 . Force, a measure of the interaction of bodies 50
51
5.3. Force is a vector . . . . . . . . . . . . . . . . . . 52
5 .4 . Vector addition and resolution of forces applied to a particle
5 5 54
Chapter 6 WEI GHT AND MASS
6. 1 . Force of gravity. Weight . 55
6 .2 . Free fall . . . . . . . 57
6 .3 . Mass of a body . . . . . 58
6.4 . The density of substances 59
Chapter 7 FUNDAMENTAL LAW OF DYNAMICS 60
7 . 1 . Force and acceleration . . . . . . . . . 60
7 .2 . Applying the fundamental law of dynamics 63
7 .3 . Weightlessness . . . . . . . . . . . 60
7 .4. System of units . . . . . . . . . . . 67
7 . 5 . The international system of units 68
7 . 6 . The cgs and mk(force)s systems of units 69
Chapter 8 EQUATIONS OF MOTION AND INITIAL CONDITIONS 69
8 . 1 . The basic problem of dynamics . . . . . . . . . . . . 69
8 .2 . Motion of a particle subject to the force of gravity . . . . 70
8 .3 . Numerical solution of the basic problem of dynamics 72
8 .4 . Motion of a body subject to an elastic force . . . . . . . 73
8.5. Quantities determining the motion equation of a particle 77
Chapter 9 GRAVITATION 78
9 . 1 . Discovery of the law of gravitation . . 78
9 .2 . Newton ' s law of universal gravitation 80
The Cavendish experiment . . . . . . . . . . . . 81
9 .4 . Determining the distances from the 'sun to the planets 82
9 .5 . The gravitational feld . . . . . . . . . . . .
9 .6 . Gravitational· feld intensity . . . . . . . . . . 84
9 . 7 . The earth 's gravitational feld . . . . . . . . . . 84
Efect of the earth's rotation of free-fall acceleration 86
Chapter 10 ELECTRIC FORCES . . . • . . .
10. 1 . Electric charge . . . . . . . . .
10 .2 . Coulomb's law . . . . . . . . . 9088
10 .3 . Units of charge and systems of units
10 .4 . The electric dipole . . . . . . .
94
10 .5 . The electric feld. Field strength . . . . . . 94
10 .6 . Electric feld of a point charge and of a dipole
Chapter 11 FRICTION 97
97
1 1 . 1 . External and internal friction
1 1 .2 . Static friction . . . . . 97
1 1 . 3 . The angle of friction . . . . 100
1 1 .4. Sliding friction . . . . . . 101
1 1 .5 . Rolling friction . . . . . . . . · . . . . . . 102
1 1 . 6 . Motion of bodies subject to the force of friction 102
1 1 . 7 . Internal friction 103
1 1 .8 . Motion of bodies in fuids 105
1 1 .9 . Bodies falling in a fuid 108
5 .2 . Elastic and plastic deformation . . . . .
9 .3 .
83
9.8 .
87
87
92
1 6 . 1 . Total energy of a body . . . .
153
1 6 .5 . Power . . . . . . . . . . .
154
1 6 . 6 . Units of energy, work and power . . . . .
155
16 . 7 . Momentum, and energy of a localized particle
157
Chapter 17 ELEMENTARY COLLISION THEORY
1 7 . 1 . What is a collision? . . . . . . . . .
17 . 2 . Completely inelastic collision . . . .
1 7 . 3 . E lastic collision . . . . . . . . . .
1 7 .4 . Neutron moderation . . . . . . . . . .
1 7 . 5 . Pressure of a stream of particles on a wall
CONTENTS 7
Chapter 12 THE THEORY OF RELATIVITY 110
1 2 . 1 . Velocity of light and the law of addition of velocities 110
12 .2 . Basic postulates of the special theory of relativity . 1 13
12 .3 . Simultaneity of events . . . . . . . . . 1 1 3
12 .4 . Simultaneity and length . . . . . . . . 1 16
1 2 .5 . Relativistic law for the addition of velocities 1 1 6
12 .6 . Limiting nature of the velocity of light 1 18
12 . 7 . Lorentz transformations . . . . . . . . 1 19
12 .8 . Length or distance . . . . . . . . . . 120
12 .9 . Time interval between two events . . . . 121
12 . 10 . The time interval between cause and efect . . . . . . . 122
1 2 . 1 1 . The relation between relativistic and Newtonian mechanics 123
<hapter 13 MASS, MOMENTUM AND FORCE IN THE THEORY OF
RELATIVITY . . . . . . . . . . . . . . . . . . . . . 125
1 3 . 1 . Relativistic mass . . . . . . . . . . . . . . . . . . 125
13 .2. The fundamental law of dynamics in the theory of relativity 126
13 .3 . The relation between Newtonian and relativistic dynamics 128
Chapter 14 EQUATIONS OF MOTION AND THE UNCERTAINTY
RELATION . . . . . . . . . . . . . . . , . . . 130
14 . 1 . Initial conditions and measuring apparatus . . . 130
14 . 2 . The uncertainty relation . . . . . . . . . . . 134
14 .3 . The uncertainty relation and classical mechanics 1 34
Part two
CONSERVATION LAWS
Chapter 15 LAW OF CONSERVATION OF LINEAR MOMENTUM 138
15 . 1 . Closed system of bodies . . . . . . . 138
15 .2 . Law of conservation of linear momentum 139
15 .3 . Recoil phenomena . . . . . . . . . 141
15.4. Measurement of mass . . . . . . . . 142
15.5. J et propulsion (propulsion by reaction) 143
15 .6 . Rocket fuel calculations . . 144
15. 7 . Centre of mass . . . . . . . . . 145
15 .8 . Motion of the centre of mass 146
Chapter 16 TOTAL AND KINETIC ENERGY 148
148
1 6 . 2 . Kinetic energy . . . . . . . 149
16 . 3 . Energy and linear momentum 150
1 6 .4 . Kinetic energy and work 151
157
158
160
162
163
Chapter 18 CONSERVATIVE FORCES AND POTENTIAL ENERGY 165
18 . 1 . Work done by a variable force . . . . . . . . . . . . 165
18 .2 . Work done by an elastic force . . . . . . . . . . . . . 167
8 CONTENTS
18 . 3 . Work done by a Coulomb force . . . . . . . . . . . . 168
18 .4 . Work done by a gravitational force . . . . . . . . . . 170
18 . 5 . Conservative forces . . . . . . . . . . . . . 171
18 . 6 . Potential energy of elastic , Coulomb and gravitational inte-
ractions . . . . . . . . . . . . . . . . . . . . . . 172
18. 7 . Potential of an electrostatic feld . . . . . . . . , . 174
18 .8 . Electric potential of the feld set up by a point charge 175
18 .9 . Energy of an electric feld . . . . . . • . . . . . . 176
Chapter 19 LAW OF CONSERVATION OF ENERGY IN NEWTONIAN
MECHANICS . . . . . . . . . . . . 177
1 9 . 1 . Mechanical energy and its conservation 177
19 . 2 . Mechanical energy and friction 177
19 .3 . Space velocities . . . . . . . . . 178
19 .4 . Looping the loop . . . . . . . . 179
19 . 5 . Potential energy curves . . . . . . 180
19 .6 . Potential energy and equilibrium 183
Chapter 20 I NTERNAL ENERGY . . . . . . 18
20. 1 . Internal energy of a system of particles . . . . . . 18
20 .2 . Changes in internal energy when a body is deformed . . . 185
20. 3 . Changes in internal energy of a body in thermal processes 186
20.4 . Changes in internal energy in chemical reactions 187
20.5 . Changes in internal energy in nuclear reactions 188
Chapter 21 THE LAW OF CONSERVATION OF ENERGY 189
21 . 1 . Work as a measure of the change in total and internal energy 189
21 . 2 . Heat exchange . . . . . . . . 190
21 . 3 . Quantity of heat . . . . . . . . 192
2 1 . 4 . The frst law of thermodynamics 193
2 1 . 5 . An adiabatically isolated system 194
21 . 6 . The law of conservation of energy 194
21 . 7 . The law of conservation of mass 195
21 . 8 . More about relativistic mass 197
Chapter 22 THE LAW OF CONSERVATION OF ANGULAR MOMEN-
TU:I . . . . . . . . . . . . . . . . . 199
22. 1 . Features of rotational motion . . . • . . . . . . . . . 199
22 . 2 . Kinetic energy and moment of inertia . . . . . . . 199
22 .3 . Dependence of the moment of inertia on the location of the
axis of rotation . . . . . . . . . . . . . . . . . . . 201
22.4. Moment of force . . . . . . . . . . . . . . . . . . . 204
22 . 5 . Equilibrium conditions for a body having an axis of rotation 205
22 . 6 . Angular momentum and the fundamental law of dynamics 205
22. 7. The law of conservation of angular momentum . . . . . 207
22 .8 . Analogies between quantities and their relations in transla-
tional and rotational motion . . . . . . . . . . . . . 209
Chapter 23 SYMMETRY IN NATURE AND THE CONSERVATION
LAWS . . . . . . . . . . . . . . . . . . . . 211
23. 1 . The conservation laws are nature 's principal laws 21 1
23 .2 . The conservation laws are forbiddenness principles 212
23.3. The conservation laws and space-time symmetry . 213
23.4 . Uniformity of time and the conservation of energy . 214
CONTENTS
Chapter 24 NONINERTIAL FRAMES OF REFERENCE AND GRA-
VITATION • • • • • . . . . • . . . . . 214
24 . 1 . Phenomena in an accelerated reference frame 214
24 . 2 . Inertial forces . . . . . . . . . . . . . . 216
24 .3 . Features of inertial forces . . . . . . . . 218
24 .4 . Space and time in noninertial reference frames 219
24 .5 . The principle of equivalence . . . . . . . 222
24 .6 . An idea of Einstein's theory of gravity 224
, 24. 7. The twin para?ox 228
Part three
MOLECULAR-KINETIC THEORY OF GASES
Chapter 25 MOLECULAR MOTION • • • . . . 231
25 . 1 . How molecular speeds were measured 231
25 .2 . Molecular speed distribution 233
25 .3 . Mean free path of molecules 235
25 .4 . Difusion . . . . . . . 238
25 .5 . Law of difusion 239
25 .6 . Separation of gas mixtures 240
Chapter 26 AN IDEAL GAS 242
26 . 1 . Gas pressure 242
26 .2 . Units of pressure 244
26 .3 . An ideal gas 246
26 .4 . Temperature . . . . . . . . . . . . . . . . . . . . 248
26 .5 . Absolute temperature and the equation of state of an ideal
gas . . . . . . . . . . . . . . . . . . . . . . . 249
26 .6 . The constant-volume gas thermometer . . . . . . . . 250
26 . 7 . The degree and the kelvin . The practical and absolute tem-
perature scales . . . . . . . . . . . . . . 251
26 .8 . Absolute zero . . . . . . . . . . . . . . 253
26 .9 . Avogadro ' s number .and Boltzmann's constant 254
26 . 10 . Molecule distribution in a force feld . . . . . 256
26 . 1 1 . Barometric distribution . . . . . . . . . 258
Chapter 27 AN I DEAL GAS AND THE F IRST LAW OF THERMODY-
NAMICS . . . . . . . . . . . . . . . . . . . . . 260
27 . 1 . Internal energy of a monatomic ideal gas . . . . . . . . 260
27 .2 . Work done in the expansion of an ideal gas . . . . . . . 261
27 .3 . The frst law of thermodynamics and the specifc heat of a gas 262
27 .4 . Isochoric processes 264
27 .5 . Isobaric processes 265
27 .6 . Isothermal processes 266
27 . 7 . Adiabatic processes 267
27 .8 . Specifc heat of a diatomic gas . . . . . . 26!
27 .9 . Quantum theory of the specifc heats of gases 272
Chapter 28 THE SECONJ LAW OF THERMODYNAMICS
28. 1 . Quasi-static processes . . . . . . . .
278
28 . 2 . Reversible processes . . . . . . . . .
28 .3 . Irreversibility of real thermal proceses
28.4 . Irreversibility and statistics . . . . . .
28 .5 . Difusion and thermodynamic probability
276
276
277
27!
282