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HigH ScHool Science Today

Textbook

FourTH year

HigH ScHool Science Today Fourth YearTextbook

Philippine Copyright 2009 by DIWA LEARNING SYSTEMS INCAll rights reserved. Printed in the Philippines

Editorial, design, and layout by University Press of First Asia

No part of this publication may be reproduced or transmitted in any form or by any means electronic or mechanical, including photocopying, recording, or any information storage and retrieval systems, without permission in writing from the copyright owner.

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ISBN 978-971-46-0103-1

reviewerBhazel Anne H. Rara-Pelicano has a bachelor’s and master’s degree in Physics from the University of the Philippines–Diliman. She is currently pursuing her doctorate degree in Physics in the same university. She has received awards and scholarships in the field of physics. Ms. Rara-Pelicano is an instructor of the National Institute of Physics at the University of the Philippines–Diliman.

PreFace

Discoveries in science and technology in recent years have had a profound impact on our society. We are now able to communicate easier with the use of the Internet and cellular phones. We have found ways to replace damaged body parts through prostheses and organ transplants. People are continually developing new medicines to treat diseases that were once fatal. Scientists have been able to clone animals, find alternative fuel sources, explore the far reaches of outer space, and develop better materials for construction. Even the way we entertain ourselves has been affected by discoveries in science.

With all these fascinating discoveries, it is important that you understand the scientific principles behind such advancements. The High School Science Today series has been developed with two objectives in mind: to explain key scientific concepts clearly and accurately within a context of unifying themes; and to introduce you to the technology and research techniques which have resulted from the application of these scientific concepts.

The topics in each textbook are organized to keep key science concepts in clear view. In each chapter, you will find discussions on specific technological breakthroughs and the implications these developments have on our global community.

Understanding science requires that you observe the things around you, perform experiments to solve problems, and explain the reasons for your observation. Each textbook contains activities that will help you develop the skills necessary in learning science concepts meaningfully. These activities will provide you with hands-on learning experiences. You will be asked to predict, hypothesize, describe, make models, form conclusions, calculate, and measure with accuracy and precision.

As such, High School Science Today will enable you to keep pace with the ever-evolving world of science and technology. We invite you to take this journey with us—into the future and beyond.

Table oF conTenTS

uniT 1 energy in SocieTy

Chapter 1 An Introduction to Physics1.1 Physics throughout Time .................................................................................... 21.2 Major Branches of Physics ................................................................................... 41.3 Physicists and Their Attitudes ............................................................................ 71.4 Mathematics in Physics ....................................................................................... 11Chapter 2 Physics, Technology, and Society2.1 Physics and Technology in Daily Life .................................................................. 192.2 Energy and Society .............................................................................................. 23

uniT 2 energy and THe environmenT

Chapter 3 Light as a Wave3.1 Wave and Its Characteristics ............................................................................... 303.2 Reflection ............................................................................................................. 343.3 Refraction ............................................................................................................. 403.4 Diffraction ............................................................................................................ 463.5 Interference .......................................................................................................... 483.6 Polarization .......................................................................................................... 49Chapter 4 Light and Vision4.1 How You See ......................................................................................................... 524.2 Eye Defects and Lenses........................................................................................ 604.3 The Eye and the Camera: A Comparison ............................................................. 634.4 Other Optical Instruments ................................................................................. 65Chapter 5 Atomic Structure and Radioactivity5.1 Atomic Physics ..................................................................................................... 705.2 Nuclear Physics .................................................................................................... 745.3 Matter-Energy Equivalence ................................................................................. 785.4 Nuclear Reactions ................................................................................................ 82Chapter 6 Uses of Nuclear Radiation in Society6.1 Effects of Nuclear Applications ........................................................................... 866.2 Uses of Radioisotopes .......................................................................................... 926.3 Radiation Safety ................................................................................................... 99

uniT 3 energy in THe Home Chapter 7 Discovery of Electricity7.1 The Discovery of Electricity ................................................................................. 1067.2 Filipinos in the Field of Electricity ...................................................................... 112

Chapter 8 Electrical Circuits8.1 Basic Parts of a Circuit ......................................................................................... 1158.2 Electromotive Force, Current, and Resistance in a Circuit ................................ 1178.3 Types of Electrical Circuit Connection ............................................................... 1208.4 Transfer of Energy in Electrical Appliances ....................................................... 128Chapter 9 Electrical Energy9.1 Measure of Electrical Consumption .................................................................... 1319.2 Electrical Conservation ....................................................................................... 1369.3 Electrical Safety .................................................................................................... 140

uniT 4 energy and THe economy

Chapter 10 Energy Generation, Utilization, Management, and Conservation10.1 Energy Resources and Development in the Philippines .................................... 14610.2 Risks of Energy Development ............................................................................. 156Chapter 11 Electricity and Magnetism11.1 Magnetic Field ...................................................................................................... 16211.2 Electromagnetic Induction .................................................................................. 16811.3 Generators and Transformers ............................................................................. 17111.4 Motor .................................................................................................................... 175 11.5 Electrical Energy Generation, Transmission, and Distribution ........................ 178

uniT 5 energy in TranSPorTaTion

Chapter 12 Development of Transportation Technology12.1 Transportation: Past to Present .......................................................................... 18812.2 Modes of Transportation .................................................................................... 18912.3 The Future of Transportation.............................................................................. 196Chapter 13 Force and Motion: Applications in Land, Air, and Sea Transport13.1 The Study of Motion ............................................................................................ 20013.2 Newton’s Laws of Motion .................................................................................... 20913.3 Law of Conservation of Momentum ................................................................... 22013.4 Pressure ................................................................................................................ 228Chapter 14 Interrelationship of Force, Power, Work, and Energy14.1 Work, Kinetic Energy, and Potential Energy ..................................................... 24314.2 Conservation of Mechanical Energy ................................................................... 25214.3 Power .................................................................................................................... 258 14.4 Machines .............................................................................................................. 26114.5 Temperature ......................................................................................................... 26514.6 Mechanical Equivalent of Heat ........................................................................... 26914.7 Expansion of Solids, Liquids, and Gases ............................................................. 27014.8 Specific Heat Capacity.......................................................................................... 27614.9 Heat of Vaporization and Heat of Fusion ........................................................... 27914.10 The Laws of Thermodynamics ............................................................................. 283

uniT 6 energy in icTChapter 15 Sound and the Development of Communication15.1 Production of Sound ............................................................................................ 29615.2 Vibration and Waves ............................................................................................ 29715.3 Characteristics of Sound Waves .......................................................................... 29815.4 Doppler Effect ...................................................................................................... 30215.5 Standing Waves .................................................................................................... 30615.6 Energy Transfer and Transformation in Communication ................................. 30715.7 Development of Telecommunication .................................................................. 310Chapter 16 Electromagnetic Theory16.1 Producing Electromagnetic Waves ...................................................................... 31816.2 Electromagnetic Spectrum .................................................................................. 32116.3 Radio Waves in Focus .......................................................................................... 32716.4 Laser and Fiber Optics ......................................................................................... 329Chapter 17 Electronic Components17.1 More on Resistors ................................................................................................ 33517.2 Capacitor .............................................................................................................. 33617.3 Conductors, Semiconductors, and Insulators .................................................... 34317.4 Semiconductor Diodes ......................................................................................... 34917.5 Transistors ........................................................................................................... 35417.6 Simple Integrated Circuits ................................................................................... 35817.7 Logic Circuits ....................................................................................................... 360

Glossary .............................................................................................................................. 371Bibliography .............................................................................................................................. 375Index .............................................................................................................................. 376

1Unit

EnErgy in SociEty

Physics is considered a basic science. It deals with universal laws and the study of the behavior and relationships of physical phenomena. In addition to its intrinsic beauty, physics also leads to an understanding of many practical applications and ideas in other areas of science. The laws of physics govern many principles of chemistry, biology, astronomy, and geology, among others.

The concepts and principles of physics constitute a major foundation of technology. Significant technological developments have been made possible through physics. For example, applications of physics in engineering and medicine have improved the quality of life. Physics affects our daily lives in more ways than one.

High School Science Today IV�

Chapter 1An introduction to PhySicS

Imagine a world without telephones, televisions, and computers. How would people communicate with one another and acquire information? Achievements in modern science and technology have made life more convenient for people. As a result, people can communicate regardless of distance, order food and pay bills over the phone, send messages electronically, and even replace a damaged internal organ.

Many tools, processes, and products have been invented and enhanced through scientific research and discoveries. Technology refers to the practical application of science upon which it is based. It is present in all sectors of society. The pace of technological progress and innovation has reached such tremendous heights that one could wonder if society can cope with these technological changes. It is important that you understand the significance or relevance of technological developments and breakthroughs in your daily life.

1.1 PhySicS throughout timE

Physics is the study of the basic interactions of matter and energy and their transformations. It is the study of the foundations of the universe from the macroscopic level (such as the universe itself) to the microscopic level (like atoms and subatomic particles). It also provides the framework in the study of other sciences. For example, physics does not teach which atoms combine to form specific compounds, but it explains why atoms behave the way they do. The study of physics can be very holistic, but you will find that many explorations on specific concepts of physics can and has led to very practical applications.

Energy in Society �

The expansion of physics has brought not only changes in ideas and acquisitions of new ones, but also a transformation of society.

Science began even before the first account of history was ever written. People learned to make predictions when they discovered patterns, regularities, and relationships in nature.

In the early part of the 17th century, Galileo Galilei agreed with the Copernican view that Earth moved around the sun. He also debunked Aristotle’s falling-body hypothesis.

Fig. 1.1 Development in the study of various sciences leads to the improvement of life

Galileo disproved the long accepted theory of Aristotle, which states that heavy objects would fall or accelerate faster than light objects. Galileo found out through his experiments that objects of different weights, when released at the same time and at the same elevation, would fall and hit the ground at the same time, except when air resistance is present. One of his experiments included rolling balls of various weights down an incline. According to legend, Galileo dropped two cannon balls from the Tower of Pisa to test his hypothesis.

At the end of the 17th century, Sir Isaac Newton made a remarkable achievement in physics when he formulated the laws of motion and gravitation.

During the 18th and the 19th centuries, electricity and magnetism were studied. In 1819, Hans Christian Oersted of Denmark discovered that a compass needle can be deflected by a current-carrying wire. Andre Ampere of France carried out a similar investigation and proved the same. A few years later, Michael Faraday of England and Joseph Henry of the United States of America further validated that electricity and magnetism are indeed related. It was during this time that James Clerk Maxwell related electricity and magnetism in one coherent theory. The nature of light as an electromagnetic wave was explained by Heinrich Hertz.

At the beginning of the 20th century, Albert Einstein’s development of the theory of relativity and his ideas on quantum mechanics marked a historic milestone in physics. Einstein’s theory of special relativity tells the nature of objects traveling at or near the speed of light, while quantum mechanics studies the behavior of subatomic particles such as electrons.


1.2 mAjor BrAnchES of PhySicS

During Einstein’s time, all fields of science were developing rapidly and their link to physics was established. Scientists realized that there had been overlaps between the different fields of science. Chemists and astronomers had to be knowledgeable about physics. Biologists had to be familiar with chemistry and physics. The integration of astronomy, chemistry, geology, and biology to physics thus became necessary.

The following are the major branches of physics:

• Astrophysics. This branch of physics deals with the physical and chemical nature of celestial objects and events. It has sometimes been defined as the application of physical laws concerning astronomical objects. Astrophysics applies the theories and methods of physics to the study of stellar structure and evolution—the origin of the solar system.

• Physicalchemistry. This branch of physics combines the principles and methods of physics and chemistry. The fundamental, theoretical, and experimental basis of organic, inorganic, and analytical chemistry is provided by the principles of physical chemistry. It is also the foundation of chemical engineering.

Physical chemistry focuses on the study of chemical equilibrium, reaction rates, solutions, molecular weights and structure, and the properties of gases, liquids, and colloids. This field considers the influence of turbulence of fluids, temperature, pressure, electricity, and light.

There are three principal approaches involved in physical chemistry. Thermodynamics involves large numbers of molecules in equilibrium. Kinetics involves chemical changes in relation to time. Molecular structure involves the electronic and atomic arrangements in which the quantum theory is applied.

Fig. 1.2 Application of geophysics in finding subsurface petroleum and other mineral deposits

• Geophysics. This is the study of the structure, composition, and dynamic changes of Earth, its lithosphere, hydrosphere, atmosphere, and magnetosphere based on the principles of physics.

Some principles of geophysics are applied in locating subsurface petroleum, mineral deposits,


and water supplies. Geophysics is also used to understand the interactions of the atmosphere and hydrosphere and how certain anomalies in the ocean’s circulation affect the atmosphere. Geophysics also explains the relation of the layers of the lithosphere to the amount and kind of subsurface water.

• Biophysics. This refers to the application of various methods and principles of physical science to the study of biological problems. It has branched out to different major divisions. In physiological biophysics, physical mechanism is used to explain biological processes such as the transmission of the nerve impulses, the muscle contraction mechanism, and the visual mechanism. Theoretical biophysics, on the other hand, tries to use mathematical and physical models to explain life processes. Radiation biophysics studies the response of organisms to various kinds of radiation for diagnostic and treatment purposes. Medical physics is the application of concepts and methods of physics to medicine, specifically, to diagnose and treat or cure human diseases.

The principles of biophysics are applied in the study of organic molecules, which play an important part in the biological processes. Paper chromatography, a direct development of adsorption techniques, is widely used to analyze tissues for chemical components. X-ray crystallography, on the other hand, is used to determine molecular structures. It has also been useful in studying the complex structure of proteins.

(a) (b)

paper

solvent

lid

solvent front

Fig. 1.3 (a) Paper chromatography and (b) X-ray crystallography

The study of biological problems requires optical methods. Among these optical methods are photochemistry, light scattering, absorption spectroscopy, and laser beams. These methods allow biophysicists to determine the structure of molecules in plants and animals to a degree not readily possible with ordinary chemical methods.


The following are the other branches of physics.

• Atomicphysics. This is the study of the properties and structure of atoms and the forces that act between the positive nuclei and the negative electrons in orbit around the nuclei.

• Electrodynamics.This is the study of the interactions between electric currents and magnetic fields created by other electric currents.

• Highenergyphysics or particlephysics.This is the study of the structure, properties, and interactions of elementary particles.

• Mechanics. This is the study of the behavior of physical systems in terms of their position in space, under the action of external forces which may be equal to or different from zero.

• Nuclearphysics. This is the study of the structure of atomic nuclei and the forces responsible for the stability or the degradation of atomic nuclei and their relation to the formation of nuclear energy.

• Optics. This is the study of the phenomena associated with the generation, transmission, and detection of electromagnetic radiation. Optics also studies light and vision.

• Thermodynamics. This is the study of the mechanical properties of matter related to energy transformations involving heat and mechanical work and how it affects matter.

Materialssmall pieces of paper with the following labels: biophysics, astrophysics, physical chemistry, geophysics, role-playing, song writing, panel discussion, and games

Procedure1. The labels will be categorized into A and B. A should include biophysics,

astrophysics, physical chemistry, and geophysics, and B should contain role-playing, song writing, panel discussion, and games.

2. The class will be divided into four groups and a representative from each group will be chosen.

3. Each representative should pick one piece of paper from A and another from B.4. Labels from B will be the activity to be completed by the group, and labels

from A will be the topic. For example, the group which has picked biophysics and role-playing should perform a role-playing activity about biophysics.

5. Each group should present its activity to the class.

Physics and Other SciencesACTIVITY


1.3 PhySiciStS And thEir AttitudES

Physicists must possess scientific attitudes that can be used in their continuous search for knowledge about how and why things behave under different conditions. Attitudes influence a physicist’s way of thinking and his/her actions. These attitudes are ways of looking at things developed through years of experience.

Physicists should be creative and curious. They make accurate observations and have the capacity to design experiments and develop hypotheses and models. They are also willing to suspend judgment until they have proven a hypothesis to be true. They are honest in reporting data and observations they have gathered. Physicists combine curiosity and imagination to obtain answers by experimentation.

Physicists carefully study and validate observations instead of disputing them right away. However, among physicists themselves and other scientists for that matter, interpretation of certain observations may differ.

Physicists are open-minded. They are willing to accept new ideas and try them out. They are also critical. They analyze and investigate the accuracy of new ideas before accepting them fully.

These positive attitudes enabled the scientific giants—Galileo, Newton, and Einstein—to discover scientific principles that improved and continues to improve human life. Today’s physicists also possess these attitudes. It allows them to help mankind and improve the

Why is it important to be knowledgeable in physics if one is to study astronomy, biology, geology, or chemistry?

Understanding the principles of physics and its applications in other fields will help you cope with the demands of today’s highly technological world. Recent developments in the field of optoelectronics, lasers, and alternative sources of energy show the practical and useful applications of the principles of physics.

quality of life. Who are some of these physicists and what are their contributions to the modern world?

FilipinoPhysicists

GregorioY.Zara,D.Sc.Physics.His important contributions include the invention of the two-way television telephone, the invention of an airplane engine that runs on alcohol, and other methods by which solar energy can be harnessed. Fig. 1.� Gregorio Y. Zara


In 1930, he discovered a basic physical law—the law of kinetic electrical resistance or the Zara effect. The law states:

“All contacts, turning or sliding, between metals, between carbon and metals, between metals and mercury, or between conductors, produce a resistance to the passage of electric current which may be kinetic and/or permanent electrical resistance. This is observed at currents of very low amperage. Kinetic electrical resistance is the resistance to the passage of electric current when contacts are in motion. Permanent electrical resistance manifests itself when contacts are at rest.”

Fig. 1.� Diosdado Banatao

Fig. 1.� Amador Muriel

Engr.Diosdado‘Dado’Banatao. His advanced chip designs were among the information technology (IT) products that helped popularize the California Silicon Valley. This chip design became the basic building blocks of the three high-tech companies he started. Among his companies are the following: Mostron, Inc., a successful manufacturer of PC motherboards; Chips and Technologies, a developer of chip-sets; and Silicon SubSystems or S3, a pioneer of the world’s first single-chip graphic user interface (GUI) accelerator. The GUI accelerator eliminates the bottleneck of the graphics subsystem, thus improving performance of computers.

He has been acclaimed for having developed the first-ever Ethernet controller chip that has enabled computers to link up and communicate with one another. This controller chip is designed to simplify the complexity of the personal computer.

Banatao was awarded the Distinguished Leadership Award by the Asian Business League, Entrepreneur Award by the Inc. Magazine, and the Ellis Island Medal of Valor by the National Ethnic Coalition of Organizations.

AmadorMuriel,Ph.D. He developed a theory addressing the turbulence observed in fluids. This theory of turbulence considers the individual molecules in the fluid. It is now being tested and examined in laboratories in France, Russia, United States, Taiwan, and Hong Kong. If the theory is proven and given practical applications, airline disasters and air disturbances would decrease and safety in air travel would be ensured. Also, understanding how turbulence works would reduce airline fuel costs by billions of dollars annually.

For these breakthroughs, Muriel has been recognized by the international scientific community. He was appointed member of the Institute for Advanced Studies in Princeton in 1997. In 1999, he was chosen as one of the Ten Outstanding Filipinos in Science.


ForeignPhysicists

Table 1.1 shows the list of the Nobel Prize Winners for physics from 1990 to 2008. Alfred Nobel, the scientist who invented dynamite in 1866, built companies and laboratories in more than 20 countries all over the world. He held more than 350 patents and even wrote poetry and drama. Nobel shared his fortune through the Nobel Foundation which he established at the beginning of the 20th century. The Nobel Prize is acknowledged as the most prestigious and the highest form of international recognition in the fields of physics, chemistry, medicine, literature, peace, and economics. The Nobel Foundation celebrated its 100th anniversary on 29 June 2000.

Table 1.1 Nobel Prize Winners for Physics from 1990 to 2008

Year Recipients Contribution

2008

Yoichiro Nambu for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics

Makoto KobayashiToshihide Maskawa

for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature

2007Albert FertPeter Grünberg

for the discovery of Giant Magnetoresistance

2006John C. MatherGeorge F. Smoot

for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation

2005

Roy J. Glauber for his contribution to the quantum theory of optical coherence

John L. HallTheodor W. Hänsch

for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique

2004David J. GrossH. David PolitzerFrank Wilczek

for the discovery of asymptotic freedom in the theory of the strong interaction

2003Alexei A. AbrikosovVitaly L. GinzburgAnthony J. Leggett

for pioneering contributions to the theory of superconductors and superfluids

2002

Raymond Davis Jr.Masatoshi Koshiba

for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos

Riccardo Giacconi for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources

High School Science Today IV10

2001Eric A. CornellWolfgang KetterleCarl E. Wieman

for the achievement of Bose-Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates

2000Zhores I. AlferovHerbert Kroemer

for developing semiconductor heterostructures used in high-speed- and opto-electronics

Jack S. Kilby for his part in the invention of the integrated circuit

1999Gerardus ‘t HooftMartinus J.G. Veltman

for elucidating the quantum structure of electroweak interactions in physics

1998Robert B. LaughlinHorst L. StörmerDaniel C. Tsui

for their discovery of a new form of quantum fluid with fractionally charged excitations

1997Steven ChuClaude Cohen-TannoudjiWilliam D. Phillips

for the development of methods to cool and trap atoms with laser light

1996David M. LeeDouglas D. OsheroffRobert C. Richardson

for their discovery of superfluidity in helium-3

1995Martin L. Perl the discovery of the tau lepton

Frederick Reines the detection of the neutrino

1994Bertram N. Brockhouse for the development of neutron spectroscopy

Clifford G. Shull for the development of the neutron diffraction technique

1993Russell A. HulseJoseph H. Taylor Jr.

for the discovery of a new type of pulsar, a discovery that has opened up new possibilities in the study of gravitation

1992Georges Charpak for his invention and development of particle detectors,

in particular the multiwire proportional chamber

1991

Pierre-Gilles de Gennes for discovering that methods developed for studying order phenomena in simple systems can be generalized to more complex forms of matter, in particular to liquid crystals and polymers

1990

Jerome I. FriedmanHenry W. KendallRichard E. Taylor

for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for the development of the quark model in particle physics

Source: Nobel Laureates in Physics (http://nobelprize.org/nobel_prizes/physics/laureates)

These people have made remarkable leaps in the realm of physics. Their discoveries led to inventions and innovations which have improved and are continuously improving our world.

Energy in Society 11

1.4 mAthEmAticS in PhySicS

Physics is a science that can show relationships between and among quantities. These relationships are expressed using mathematical equations.

SignificantFigures

Significant figures include numbers which can be read clearly from the scales of the measuring instrument plus a last uncertain number which is estimated between the smallest scales of the instrument. It is important that measurements taken be expressed in the proper number of significant figures. The following are rules to be followed in determining the number of significant figures:

Rule 1. All nonzero digits are always significant.Examples: 72 465 five significant figures 7 246.5 five significant figures

Rule 2. A zero between nonzero digits is always significant. Examples: 903 three significant figures 90.3 three significant figures

Rule 3. A trailing zero after a decimal point is significant.Examples: 4 625.0 five significant figures 462.50 five significant figures 0.610 three significant figures 0.6100 four significant figures

Rule 4. A zero used to fix a decimal point in a number less than 1 is not significant.Examples: 0.1256 four significant figures 0.01256 four significant figures

Rule 5. A zero ending a number more than 1 may or may not be significant.Examples: 760 000 may have two to six significant figures

The ambiguity of this last rule can be resolved by expressing these numbers in scientific notation.

7.6 × 105 two significant figures 7.600 × 105 four significant figures

High School Science Today IV1�

ScientificNotationandMeasurement

Very large and very small numbers can be conveniently expressed as powers of 10. The number written to the right and above the figure 10 is called an exponent. The scientificnotation is the system of expressing products with a number between 1 and 10 multiplied by an appropriate power of 10. A positive exponent tells how many times a number must be multiplied by 10 to obtain a certain number. For example, 1 × l03 means 1 should be multiplied by 10 three times, i.e., 1 × 10 × 10 × 10 equals 1 000. Conversely, 1 × 10–5 means to divide 1 by 10 five times. Therefore, 1 × 10–5 equals 0.00001. Note that 0.00001 should contain the same number of significant figures as 1 × 10–5. The number to be multiplied by 10 should always be between 1 and 10.

Measurement is the process of comparing a specific quantity of matter with an agreed standard. It is a method of describing physical phenomena. There are two kinds of quantities of measurements: fundamental and derived. Fundamental quantities can be measured directly using specific instruments. Derived quantities are based on fundamental measurement. They can be a combination of fundamental quantities or a combination of fundamental and other derived quantities.

In science, the system of measurement used is the International System of Units or the SI (Systeme Internationale d’ Unites). It was adopted for worldwide use in 1960.

PrecisionandAccuracy

In measurement, accuracy and precision are required. The terms precision and accuracy have different meanings. The precision of a measurement is the degree of agreement between different values obtained under basically the same condition. It is a measure of the degree to which measurements agree.

A measurement is said to have a high degree of precision when independently obtained values closely agree. That is, when several trials are done under the same condition, the numerical data that are obtained are very close to one another.

For example, three of your classmates were asked to measure the length of a pencil. They obtained the following results: 9.60 cm, 9.70 cm, and 9.60 cm. You can say that the values obtained are precise because the values are close to one another.

Accurate but imprecise Inaccurate but precise

Inaccurate and imprecise Accurate and precise

Fig. 1.� Accuracy versus precision

Energy in Society 1�

The accuracy of a numerical result is the degree of agreement between the experimental result and the true value. It is quite possible in duplicate measurements to have highly similar results while at the same time both could be far from the true value. An error of approximately the same measure may be involved in each.

For example, the length of a pencil is 9.65 cm. This is the true value. Our experimental results are 9.60 cm, 9.70 cm, and 9.60 cm. If you get the average of these experimental results, which is 9.63 cm, you will see that the results are accurate because it is close to the true value.

Many factors affect the precision and accuracy of experimental results. These factors include condition of equipment, quality of material used, and environmental conditions such as temperature and pressure.

FundamentalQuantitiesofMeasurement

Below are the seven fundamental quantities of measurement and the corresponding SI units.1. Length is the measure of distance from one point to another. The SI unit of length is

meter (m). Meter was redefined in 1983 as the distance that light traveled in a vacuum

during a time interval of 1 299 792 458 of a second. Rulers, metersticks, tape measures,

vernier calipers, and micrometer calipers are used to measure length.2. Mass is the measure of the quantity of matter in a body. The SI unit used to express

mass is kilogram (kg). The standard kilogram is a block of platinum-iridium alloy, which is preserved at the International Bureau of Weights and Measures in France. A spring balance or scale can be used to measure mass.

3. Time is the measure of duration or the interval between two events or phenomena. The SI unit of time is second (s). Instruments such as clocks and stopwatches are used to measure time.

4. Temperature is the measure of the average kinetic energy of all molecules of a given substance. The SI unit of temperature is Kelvin (K). Thermometers are used to measure temperature.

5. Luminousintensity is the measure of radiant intensity in a given direction. It also pertains to the brightness of light. Its SI unit is candela (cd). Radiometers and photometers are used to measure luminous intensity.

6. Electriccurrent is the measure of flow of electrical charges. The SI unit of electric current is ampere (A). An ammeter is used to measure electric current.

7. Mole (mol) is the amount of substance which contains as many entities as there are atoms in 0.12 kilogram of carbon 12. Specifically, it is defined using Avogadro’s number, whose value is 6.02 × 1023 molecule/mol.


DerivedQuantitiesofMeasurement

1. Area is the amount of surface usually expressed in square meters (m2).

Arectangle= lw Asquare= s2 Atriangle = 12

bh Acircle = r2

where A = area, l = length, w = width, s = side, b = base, h = height, and r = radius. The symbol π (pi) has a value of 3.1416 (estimated to four decimal places).

2. Volume is the total space occupied by a body. Its SI unit is the cubic meter (m3). Vrectangular prism = lwh Vcylinder = πr2h

where V = volume and r = radius

3. Density is the ratio of mass to volume of a given material. Its SI unit is kilogram per cubic meter (kg/m3).

= m

V

where = density, m = mass, and V = volume

4. Speed is the distance traveled by an object per unit time. Its SI unit is meter per second (m/s).

v = d t

where v = speed, d = distance, and t = time

5. Acceleration is the rate at which the velocity (a rate of change in position in a particular direction) of a moving body changes. The change in velocity may be in magnitude (speed), direction, or both. It is measured in meter per second squared (m/s2).

a = ∆v ∆t

where a = acceleration, ∆v = change in velocity, and ∆t = change in time

6. Weight is the pull of gravity in an object. It is expressed in newtons (N). One newton is equal to 1 kg · m/s2.

w = mg

where w = weight, m = mass, and |g| = the magnitude of the acceleration due to gravity which is equal to 9.8 m/s2.

SI provides prefixes which can be used with SI units. Table 1.1 lists the 20 approved SI prefixes.


Table 1.2 Prefixes for Powers of 10

Number Factor Name Symbol

1 000 000 000 000 000 000 000 000 1024 yotta Y

1 000 000 000 000 000 000 000 1021 zetta Z

1 000 000 000 000 000 000 1018 exa E

1 000 000 000 000 000 1015 peta P

1 000 000 000 000 1012 tera T

1 000 000 000 109 giga G

1 000 000 106 mega M

1 000 103 kilo k

100 102 hecto h

10 101 deca da

0.1 10–1 deci d

0.01 10–2 centi c

0.001 10–3 milli m

0.000 001 10–6 micro µ

0.000 000 001 10–9 nano n

0.000 000 000 001 10–12 pico p

0.000 000 000 000 001 10–15 femto f

0.000 000 000 000 000 001 10–18 atto a

0.000 000 000 000 000 000 001 10–21 zepto z

0.000 000 000 000 000 000 000 001 10–24 yocto y

The SI units were developed to replace the English system of measurement because of the complexity in converting from one unit to another using the English system. Yards, ounces, inches, and quarts are units in the English system.


Today, we still use a few units from the English system such as inches, miles, and feet. A conversion table was developed to facilitate conversion from the English system to the metric system and vice versa. Table 1.3 lists common conversion factors for the two systems of measurement.

Table 1.3 Conversion Factors of the English and Metric Systems of Measurement

LengthandVolume

1 in 2.54 cm

1 ft 0.3048 m

1 m 39.37 in

1 mi 1.6093 km

1 L 103 cm3 or 10–3 m3

Mass

1 kg 2.2 lb

SampleProblems:

1. Annie is 5 ft 4 in tall. What is her height in meters? Solution:

5

12 in= 60 inft

ft×

1

5 ft 4 in = 5 ft + 4 in = 60 in + 4 in = 64 in

64 in

2.54 cm1

1 m

100= 1.6 m×

in cm×

2. What is the equivalent of the density of aluminum (2.7 g/cm3) in kilogram per cubic meter?

2.7 g 1 kg1 000

100 cm

1 m = 27 000 kg/ m3

3

cm g3 × ×

( )3

= 2.7 10 kg/ m4 3×

Observe that in problem 2, the answer has the same number of significant figures as that of the given. This should be done in converting one unit of measure to another.


Exercises:

1. Find the density of a book which measures 25 cm × 20 cm × 1.8 cm and has a mass of 0.5 kg.

2. Elai is 180.02 cm tall. Express her height in meters.

You now see the reason why having a good background in mathematics is important in physics. Many physicists excel in mathematics like Isaac Newton. His book Principia was a pioneering work in the field of mathematical physics. Some of Newton’s contributions include the law of gravitational attraction, the discovery of the nature of white light, and the development of differential and integral calculus.

Using his discoveries, Newton was able to further work out the details of Earth’s motion, accurately estimate the mass of the sun and Earth, prove that tides were the result of the moon’s gravitational attraction, explain the orbits of comets, and lay the foundation for the treatment of wave motion.

Accurate measurements are obtained when the instrument is properly calibrated and a correct reading is made.


I. EnrichingYourScienceVocabulary

Choose from the words inside the box the term that is being described in each phrase below.

measurement biophysics accuracy speedacceleration astrophysics technology volumedensity weight precision scientific notation

__________ 1. deals with the physical and chemical nature of celestial objects and events

__________ 2. refers to the application of various methods and principles of physical science to the study of biological problems

__________ 3. process of comparing a specific quantity of matter with an agreed standard

__________ 4. rate at which the velocity of a moving body changes__________ 5. pull of gravity in an object __________ 6. distance traveled by an object per unit time __________ 7. ratio of mass to volume of a given material __________ 8. degree of agreement between several values obtained basically

under the same conditions__________ 9. practical application of science__________ 10. extent to which a measured value agrees with the standard value

of a quantity

II. AssessingYourKnowledge

A. Match the scientist with his or her achievement. Write the letter of your answer.

_____ 1. Isaac Newton

_____ 2. Albert Einstein

_____ 3. Galileo Galilei

_____ 4. Heinrich Hertz

_____ 5. James Clerk Maxwell

B. Convert the following. 1. 10 mi to km 3. 86 km to m 2. 300 cm to ft 4. 45 in to cm

a. formulated the laws of motion and gravitation

b. explained the nature of light as an electromagnetic wave

c. postulated the theory of relativityd. combined electricity and magnetism

into one coherent theorye. disproved the theory that heavy objects

fall or accelerate faster than light objects

Chapter Review

Hssttx4

Technology

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