Table Of ContentStudent's
Guide
Physics
in the
Modern
World
Jerry B. Marion
University of Maryland
College Park
Academic Press New York / San Francisco / London
A Subsidiary of Harcourt Brace Jovanovich, Publishers
COPYRIGHT © 1976, BY ACADEMIC PRESS, INC.
ALL RIGHTS RESERVED.
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ISBN: 0-12-472278-4
PRINTED IN THE UNITED STATES OF AMERICA
To The Student
This Guide is designed to help you in your study of the science of
physics using Physios in the Modem World. As you proceed through the text
material, you may wonder which are the really important topics, ideas, equa
tions, and numbers. In this Guide you will find, for each chapter, a list
of the Objectives for that chapter. You should look carefully at these lists
as you read the chapters so that you will be able to identify the important
points. You can test your understanding of the material by answering the
supplementary questions and working the supplementary exercises that are
given for each chapter. The answers to the various questions are given at
the end of each chapter.
If you are pursuing a self-paced course, the lists of objectives and the
questions and exercises for each chapter should assist you in preparing for
the unit examinations that your instructor will use to gauge your progress.
Also in this Guide you will find, for each chapter, a list of Readings.
These are not merely references to other textbooks — you will have no dif
ficulty locating such material. Instead, the books listed here emphasize
historical, biographical, and popular accounts of the topics in the text. A
large fraction of the books are available in paperback editions. There are
also numerous magazine articles that are useful sources of supplementary
reading material. However, the lists here include only articles in
Scientific American because this magazine is widely available and contains
articles on a great variety of scientific topics, and because the level of
presentation is such that students in introductory physics courses will be
able to understand most of every article.
vii
Chapter 1
Introduction to Physical Ideas
Objectives
Things you should understand and know how to do in Chapter 1:
1. You should know that the fundamental units of measure in science are
those of length, time, and mass* All other quantities (such as den
sity, energy, force, pressure, and so forth) can be expressed in terms
of these three fundamental quantities.
2. You should know that the metric system of measure is based on the
standard units of the meter, the kilogram, and the second (the MKS
system).
3. You should remember these metric multiples:
1 m = 100 cm
1 cm = 10 mm
1 km = 1000 m
1 kg = 1000 g
4. You should remember these conversion factors:
1 in. = 2.54 cm
1 lb = 0.454 kg (or 1 kg = 2.2 lb)
5. You should be able to convert from any British unit of length or mass
to the equivalent metric unit and vice versa. For example, from miles
to meters by using 1 mi = 5280 ft, 1 ft = 12 in., 1 in. = 2.54 cm, and
100 cm = 1 m.
6. You should be able to express any number in terms of powers of ten.
5 4
For example, 140 000 = 1.4 χ 10 and 0.00013 = 1.3 χ 10" .
7* You should be able to multiply and divide using powers of ten. For
3 4 7 4 6
example, (2 χ 10 ) χ (3 χ 10 ) = 6 χ 10 , (4 χ 10 ) χ (2 χ 1θ") =
2 6 2 4
8 χ 10" , and (6 x 10) * (3 χ 10) = 2 χ 10 .
1
CHAPTER 1
8. You should be able to estimate and express the sizes of some everyday
things in terms of metric units and powers of ten.
-2
For example, the width of a finger is about 1 cm = 10 m; the volume
3
of an ordinary bedroom is about 4 m x 4 m x 3 m = 4 8m .
9. You should understand the reason for the adoption of atomic standards
of measure for length and time. You should understand why the kilogram
cannot yet be specified in terms of an atomic standard.
10. You should remember the definition of density; density is mass per unit
volume, ρ = M/V. If you are given any two of the three quantities in
this expression, you should be able to calculate the remaining
quantity.
11. You should have a rough idea of the density of some everyday things.
3
(It is probably easier to think about densities in g/cm because the
3
density of water is 1 g/cm . Remember this value.)
Important Equations and Numbers
Conversion factors: 1 in. = 2.54 cm
1 lb = 0.454 kg
M
Density: ρ = ~
2
CHAPTE R 1
Examples
1 . I n etpahC r 6 w e wil l nif d aht t ht e anoitativarg l crof e o n a n cejbo t o f
mas s ecudorp d b y a n cejbo t o f mas s i s
M M
± 2
F = G
wher e r i s ht e cnatsid e betwee n na d M^. hT e inu t o f F i s ht e
2
kg-m/s . ahW t i s ht e inu t o f GÏ
noituloS :
nivloS g of r G w e vah e
9
2
F χ r
G = MM
12
so that the unit of G is the
2 2
(kg-m/s) χ m 3 2
^-f——|-* = m 7/ lkg-s
kg x kg
2. Express 1 cm/s in miles per year (mi/y)
Solution :
1 cm _ ., cm * 1 in. Ί ft 1 mi '
s 1 s— X 2 .54 cm 12 in. 5280 ft
3600 s 24 h 365 days
X 1 h 1 day ι
y
= 197 mi/y
3
CHAPTER 1
3. Calculate the height of a cylinder of radius 3 cm, which has a mass of
3
500 g and a density of 4 g/cm .
Solution;
ρ = y and V = ττν η so
9
TW h = —
Ρ
Therefore,
^2 = — ——2 — ... . . ,,^ι -, „ ^2Ρ. 3 ~ 4.43 cm
τπτ»ρ (3.14) (3 cm)(4 g/cm )
J. Β. Conant, Science and Common Sense
(Yale University Press, New Haven, Conn., 1951).
G. Gamow, One, Two, Three ... Infinity
(Viking, New York, 1962).
C. C. Gillespie, The Edge of Objectivity
(Princeton University Press, Princeton, N. J., 1960).
S. A. Goudsmit and R. Claiborne, Time
(Time, Inc., New York, 1966).
H. Margenau and D. Bergamini, The Scientist
(Time, Inc., New York, 1964).
M. A. Rothman, Discovering the Natural Laws
(Doubleday, Garden City, Ν. Y., 1972).
P. Tompkins, Secrets of the Great Pyramid
(Harper and Row, New York, 1971). An interesting commentary on
ancient Egyptian metrology; the last few chapters, however, are
sheer numerology.
A. M. Weinberg, Reflections on Big Science
(M.I.T. Press, Cambridge, Mass., 1967).
Scientific American articles:
Α. V. Astin, "Standards of Measurement," June 1968.
J. Cohen, "Psychological Time," November 1964.
H. Lyons, "Atomic Clocks," February 1957.
Lord Ritchie-Calder, "Conversion to the Metric System," July 1970.
4
CHAPTER 1
Supplementary Questions and Exercises
1. In the metric system, length, time, and mass are measured in
(a) foot, second, and pound*
(b) foot, second, and kilogram·
(c) meter, minute, and kilogram.
(d) meter, second, and kilogram.
2. Which of the following is not correct?
2 4
(a) 0.014 = 1.4 χ 10 (b) 13760 = 1.3760 x 10
4 6 4
(c) 127 x 10 = 1.27 χ 10 (d) 0.000078 = 0.78 x 1θ"
3. Write the following in powers-of-ten notation:
(a) 137650 (b) 162.78
(c) 0.00037 (d) 100 000 000 000
4. Since 1967 the international standard of time has been based on
(a) rapidly vibrating quartz crystals .
(b) the light emitted by krypton atoms .
(c) vibrations of cesium atoms.
(d) a vibrating tuning fork.
5. How old are you in seconds? (Do not neglect leap years.)
6. A facetious unit of speed is furlongs/fortnight. Express this in mi/h
and in cm/s. (A furlong is 220 yards and a fortnight is 2 weeks.)
5
CHAPTER 1
What is the advantage of having atomic standards for length and time,
compared with arbitrarily defined standards?
8. How many grams are in a ton? (1 ton = 2000 lb)
9. Which of the following is approximately correct?
4
(a) 1 day = 10 s (b) 5 kg = 11 lb
(c) 3 mi = 2 km (d) 1 ft = 15 cm
3 4 3
10. What is the mass of 100 cm of mercury (p = 1.36 x 10 kg/m )?
11. Density is defined as the ratio
ζ ν mass ν volume
(a) —- (b) /Λ
volume mass
m
(U ;\ ass }volume K
length length
12. Arrange the following list according to increasing density:
steel, oil, cork, lead, rock.
6
CHAPTER 1
13. Given two objects and told that the objects have the same density,
which one of these statements must be true?
(a) The volume is the same for both objects.
(b) The mass is the same for both objects.
(c) If the objects are cylindrical, they have the same diameter.
(d) If one object has twice the volume of the other object, it also
has twice the mass.
14. A crystal cube has sides which are 11.5 mm long. If the mass of the
3
crystal is 3.5 g, what is its density expressed in g/cm ?
15. Suppose that you have 2 blocks of gold, one with a mass of 2 kg and
the other with a mass of 5 kg. What is the density of each?
7
