Study Guide for Physics in the Modern World 2E

By Jerry Marion

Study Guide for Physics in the Modern World 2E provides information pertinent to the fundamental concepts in physics. This book presents a list of concepts, definitions, and equations with various supplementary exercises for the readers. Comprised of 21 chapters, this book starts with an overview of the standard units of measure for length, time, mass, energy, force, pressure, and density. This text then provides the meaning of various terms in physics, including atom, molecule, element, and compound. Other chapters explore the composition and behavior of all ordinary matter in which it depends on the four basic units, including electrons, protons, neutrons, and photons. This book discusses as well the method used for converting the units of physical quantities from one system of measurement to another. The final chapter deals with the various applications of radiation in biological investigations as well as in medical diagnostics and therapeutics. This book is intended for students enrolled in introductory physics courses.

• Language: English
• Publisher: Academic Press
• Release date: Dec 2, 2012
• ISBN: 9780323160681

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CHAPTER 1

INTRODUCTION TO PHYSICAL IDEAS

Publisher Summary

This chapter presents an introduction to various physical notions, such as density, energy, and force. The task of physics is to investigate and comprehend the universe on a microscopic scale, such as atoms and molecules and on a macroscopic scale, such as everyday objects. It explains the three fundamental units of measure, which are length, time, and mass. The standard units of the metric system are the meter, the kilogram and the second, which is the MKS system. The chapter reviews the atomic standards of measure, and illustrates the calculation of density. It also presents how to estimate and express the sizes of some everyday things in terms of metric units and powers of 10.

CONCEPTS, DEFINITIONS, AND EQUATIONS

1. The task of Physics is to investigate and understand our Universe both on a microscopic scale (atoms and molecules) and on a macroscopic scale (everyday objects, planets, etc.)

2. The units of measure for all mechanical quantities (density, energy, force, etc.) can be expressed in terms of the three fundamental units of measure: length, time and mass.

3. The standard units of the metric system are the meter, the kilogram and the second (the MKS system).

4. Metric multiples most commonly used are:

1 m = 100 cm

1 cm = 10 mm

1 km = 1000 m

1 kg = 1000 g

5. Be able to convert from any British unit of length or mass to the equivalent metric unit and vice versa.

For example, convert miles to meters by using 1 mi = 5280 ft, 1 ft = 12 in., 1 in. = 2.54 cm, and 100 cm = 1 m.

6. Be able to express any number in terms of powers of ten and to multiply and divide by using this notation.

For example, 140,000 = 1.4 × 10⁵, 0.00013 = 1.3 × 10−4; (2 × 10³) × (3 × 10⁴) = 6 × 10⁷; (6 × 10−5) ÷ (3 × 10−8) = 2 × 10³

7. You should be able to estimate and express the sizes of some everyday things in terms of metric units and powers of ten.

For example, the width of a finger is about 1 cm = 10−2 m; the volume of an ordinary bedroom is about 4 m × 4m × 3m = 48 m³

8. 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.

9. 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.

10. You should have a rough idea of the density of some everyday things.

(It is probably easier to think about densities in g/cm³ because the density of water is 1/cm³. Remember this value.)

Important Equations and Numbers

Examples

1. In Chapter 6 we will find that the gravitational force on an object of mass M1 produced by an object of mass M2 is

where r is the distance between M1 and M2. The unit of F is the kg-m/s². What is the unit of G?

Solution:

Solving for G, we have

so that the unit of G is the

2. Express 1 cm/s in miles per year (mi/y).

Solution:

3. The Earth-Sun distance is 150,000,000 km. Express this distance in: (a) centimeters, (b) feet.

Solution:

(a) 

(b) 

(g = acceleration of gravity in m/s², l = length in m)

Solution:

5. What is the mass in pounds of 500 g of nails?

Solution:

6. Calculate the height of a cylinder of radius 3.0 cm, which has a mass of 500 g and a density of 4.0 g/cm³.

Solution:

    Therefore,

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?

(a) 0.014=1.4 × 10²

(b) 13760 = 1.3760 × 10⁴

(c) 127 × 10⁴ = 1.27 × 10⁶

(d) 0.000078 = 0.78 × 10−4

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.)

7. 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?

(a) 1 day ≅ 10⁴ s

(b) 5 kg ≅ 11 lb

(c) 3 mi ≅ 2 km

(d) 1 ft ≅ 15 cm

10. What is the mass of 100 cm³ of mercury (ρ = 1.36 × 10⁴ kg/m³)?

11. Density is defined as the ratio

.

.

.

.

12. Arrange the following list according to increasing density: steel, oil, cork, lead, rock.

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 crystal is 3.5 g, what is its density expressed in g/cm³?

15. Suppose that you have 2 blocks of gold, one with a mass of 2.0 kg and the other with a mass of 5.0 kg. What is the density of each?

Answers to Supplementary Questions and Exercises

1. (d)

2. (a)

3. (a) 1.3765 × 10⁵, (b) 1.6278 × 10², (c) 3.7 × 10−4, (d) 10¹¹

4. (c)

5. −

6. 3.7 × 10−4 mi/h; 1.6 × 10−2 cm/s

7. Because all atoms are exactly alike, the required standard can be established in any laboratory where it is needed, and it is guaranteed that all such standards will be absolutely identical. Also, atomic standards are extremely accurate.

8. 9.08 × 10⁵ g

9. (a), (b)

10. 1.36 kg

11. (a)

12. cork, oil, rock, steel, lead

13. (d)

14. 2.53 g/cm³

15. 1.93 × 10⁴ kg/m³; both blocks have the same density.

Readings

Conant, J.B.Science and Common Sense. New Haven, Conn.: Yale University Press, 1951.

Gamow, G.One, Two, Three … Infinity. New York: Viking, 1962.

Gillespie, C.C.The Edge of Objectivity. Princeton, N. J.: Princeton University Press, 1960.

Goudsmit, S.A., Claiborne, R.Time. New York: Time Inc., 1966.

Margenau, H., Bergamini, D.The Scientist. New York: Time Inc., 1964.

Rothman, M.A.Discovering the Natural Laws. Garden City, N. Y.: Doubleday, 1972.

Tompkins, P.Secrets of the Great Pyramid. New York: Harper and Row, 1971. [An interesting commentary on ancient Egyptian metrology; the last few chapters, however, are sheer