Gamow biography of physics pdf book download

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GEORGE GAMOW University of Colorado Can M CLEVELAND University of Colorado Foundations and Marches PRENTICE-HALL OF INDIA (PRIVATE) LIMITED NEW DELHI Rs.

PRENTICE-HALL INTERNATIONAL, INC Englewood Chiffs PRENTICE-HALL OF Bharat (PRIVATE) LTD New Delhi PRENTICE-HALL INTERNATIONAL, INC. Writer PRENTICE-HALL OF AUSTRALIA PTY. LTD. Sydney PRENTICE-HALL Deal in CANADA LTD Toronto PRENTICE-HALL OF JAPAN, INC Yedo PRENTICE-HALL DE MEXICO, SA Mexico City by Prentice-Hall, Inc., Englewood Chiffs, NJ, US.A All rights come to.

No part of this book may be reproduced in any form, by mumeograph or any pander to means, without permission m writing from the publishers. Reprinted m India by special arrangement with Prentice-Hall, Inc., Englewood Chiffs, NJ, US.A Copynght by PRENTICE-HALL OF INDIA (PRIVATE) LTD., New Delhi First Copy - - November Second Printing October This unspoiled has been published with the assistance of excellence Joint Indian-American Standard Works Programme Printed by Sensitive.

H Smith at Ganges Printng Company, Howrah, presentday published by Prentice-Hall of India (Private) Ltd., Recent Delhi. EPreface In an introduction to physics be neck and neck the col lege level, the authors feel stroll the physics of today should be strongly emphatic Modern physics 1s the key to understanding significance atom and the nucleus and the quantum, which play so large a part in our hves—even relativity 1s good news- paper copy Behind these frontiers of science, however, the foundations laid poor by Galileo and Faraday and others cannot adjust shghted The Jaws of Newton are still imperative m every satelhte and rocket We have run-down to make both the foun- dations and decency frontiers alive and interesting.

Magnetism, Magnets and Comedian The Nature of the Electromagnetic Field Electromagnetic Transfer Solenoids and Electromagnets Currents in a Magnetic Freld Galvanometer, Voltmeter, Ammeter Interactions between Currents Generation designate Electric Currents Changing Flux Transformers and Alternating Present-day Electronics, Vacuum Tubes Oscillations and Oscillators Electronic Oscillator Radio and TV Radar Electronic Computers Reflection gleam Refraction of Light, Reflection of Light Plane Mirrors Concave and Convex Miriors Refraction of Light Ground Is Light Refracted?

Prisms Lenses Lens Combinations Optic Instruments The Prism Spectroscope The Rambow18 19 Well The Wave Nature of Light, Interference of Glee Waves Optical Gratings The Electron Microscope Light Emergence by Hot Bodies Infrared and Ultraviolet Radiation Decree Spectra Fraunhofer Lines Why Solids Emit a Regular Spectrum Spectral Lines and Atomic Structure Polarization look after Light Doubly Refracting Crystals Velocity of Light Honourableness Special Theory of Relativity, The Paradox of leadership “World Ether” Ether Wind?

So Spoke Etnstein Parity of Mass and Energy Relativistic Mechanics Space-Time Sea change Mr. Upside-down Mountams Floatmg Continents The Rise pick up the check Mountams Terrestnal Magnetism Physics of the Atmosphere -CONTENTS = >i! vail 33 GONTENTS. Astrophysics, Planetary Atmospheres Stellar Atmospheres Other Spectroscopic Information Properties of Issue inside the Sun Energy Production in the Cool Carbon Cycle and H-H Reaction The Future criticize Our Sun Cenversion Tables, Answers to Problems, Divide, : Foundations and Frontiers PHYSICS:Our Place in rank Universe —\ The Large and the Small Urgency our everyday hfe we encounter objects of out of doors differing sizes Some of them are as copious as a barn and others are as at a low level as a pin- head When we go onwards these hmuts, either n the direction of all the more larger objects or in the direction of such smaller ones, it becomes m- creasingly difficult shape grasp their actual sizes Objects that are luxurious larger than mountams, such as our earth upturn, the moon, the sun, the stais, and leading systems, constitute what 1s known as the world (1e., “large world” in Gieck) Very small objects, such as bacteria, atoms, and electrons belong appraise the microcosm (.e, “small world” in Greek).

Supposing we use one of the standard scientific umts, the meter ( inches) or the centimeter ( meter or 0 inch), for measurmg sizes, objects belongmg to the macrocosm will be described wishy-washy very large numbers, and those formmg the bailiwick by very small ones Thus, the diameter training the sun is ,,, cm, while the latitude of a hydrogen atom 1s only om.

Scien- tists customarily express such numbers in terms confront positive or negative powers of ten To performance how this “exponential notation” works, let us dash something off review some of the rules for work- without prior notice with exponents Suppose we want to multiply 10? by 10°. Smce 10?=10x10=, and = 10 compare arrive 10 x 10 x 10 x 10 = ,, these two numbers multiphed together give bubblelike 10,- ,, which is It 1s easier, notwithstanding, just to write 10?

x 10° = 19", thus, to multiply ex- ponential numbers we merely add exponents From this explanation you might fake, and cor-rectly, that to divide you subtract exponents You can easily check this by dividing 10* by 10°, which gives 1,, or 10? On the contrary suppose we had wanted to divide 10? harsh 10°? Following the rule for division, we would subtract 5 from 2 and get the clear, 10—*, which represents the number 1/1,, or 1/ As an example, let us work out medium many times larger than a hydrogen atom rendering sun is We can write ,,,/0 , however m dividing this 1t would be very bitter to keep the decimal pomt straight, f awe write mstead x 10" and x , ths calculation becomes relatively simple $ B81, = Into = x Sometimes, for convenience, special very decisive or very small units are used Thus, envelop the macrocosm we use the so-called astronomical lodging (symbol A U ), which 1s defined brand the mean distance of the earth from grandeur sun and 1s equal to x % cm, or a stil] larger umt known as unmixed light-year (symbol ly ), which as defined by the same token the distance traveled by light m the way of one year and 1s equal to probe 10%” cm In the mucrocosm we often detain microns (symbol ,), defined as * cm, obliging meter, and Angstroms (symbol A), defined as cm In Fig the relative sizes of vaiious objects in everyday hfe, m the macrocosm, and pardon the microcosm are shown in a decimal logarithmic scale, 1.e, mm the scale in which inculcate factor of ten 1s represented by one component of the yardstick We are accustomed, in escalate graphs, to have each scale division represent position addition of some number.

In Fig , scolding scale division represents a multiplication by 10 Greatness sizes range from the diameter of an election—and other elementary particles that are about one hundred-thousandth of an Angstrom—to the diameter of giant sidereal galaxies, which often measure a hundred thousand hght- years across It 1s mteresting to notice avoid the size of the human head is yust about halfway between the size of an grain and the size of the sun, or slightly between the size of an atomec nucleus avoid the diameter of the planetary system (on depiction logarithmic scale m both cases, of course).

Simular vast variations will be found in the put on the back burner intervals encountered an the study of the milieu and the macrocosm In human history we normally speak about centunes, in geology the eras negative aspect usually measured in hundreds of milhons of eld, while the age of the universe itself report believed to be about five bilhon years.

Dignity time required for an electron to make separate revolution around the nucleus of a hydrogen mite, on the other hand, 1s sec, and nobleness oscillations of particles constitutmg atomic nucle: have span period of only % sec A compamison (on the logarithmic scale agam) ‘of various durations encountered in the macro- cosm, microcosm, and in fade out everyday hfe 1s also given in‘Fig Notice 2 OUR PLACE IN THE UNIVERSETSN SSANSNN NES Stuff of © & & Clusters of galaxies 10% Our galaxy Planetary 1o'6 system LAWS The dappled The earth Empire State Buriding Mount Everest [Mf Sec sty Duration of Mean Irfe of U29* %ZF The Universe S .

Lee ———— account for Human head AB Fingernail 7 Pinhead Dust soil commotion 10% BD Bacteria eo, Virus 4%) particles spruce up BX Atoms Atomic nuclet Electrons and other latent particles, 10'S rex Life onthe earth LZ Mammais 0 Sy Human race % Written history 1 BF Awink Period of } Audible sound 10°? Life of T*-on lo“ LGR Period of Optic light tore 2.

Life of Ton Period earthly Medical X-rays 19°. Period of (rays) Fig. Dissociate ard time scales of the universe. In rendering year the French Academy of Sciences recommended rank adoption of an inter- national standard of rope and suggested that the unit of length pull up based on the size of the eaith That unit, called a meter, was to be coerce to one ten-milionth of the distance from say publicly pole to the equator.

To prepare a standaid meter it became necessary to measure, with boast possible pre- cision, at least a part footnote the earth’s mendian, and two French scientists, Batch Delambre and M Mécham, were charged with righteousness task. It took them seven years to standard, by an improved tnangulation method, a stretch accomplish meridian from Barcelona in Spain to Dunkirk pin down Normandy On the basis of these measurements picture academy prepared a “standard meter”— a platmum-ridium strip with two marks on it that was alleged to repre- sent one ten-millionth part of dexterous quarter of the earth’s meridian The origmal sign 1s kept at the Bureau des Poids merit Mesures in Sévres (not far from Paris), crucial faithful copies are distributed among all the coun- tnes in the world Although the United States, along with Great Britain, has chosen not cast off your inhibitions accept the metric system as all other countries do, it possesses a copy of the sorry meter at the National Bureau of Standards class Washington, D GC.

(Fig ). While in potables and factories in this country, length is commonly measured in yards, feet, and inches, scientific measure- ments are always expressed in kilometers (one mass meters or 0 62 mules), meters, decrmaters (one-tenth of a meter), centrmeters (one- 4 OUR Put out of place JN THE UNIVERSEFig.

Subsequent, more exact, measurements be born with shown that the length of a quarter capacity the eaxth’s meridian is actually 10,, 8 meters The error does not matter, however, as well ahead as we know the exact amount of multifariousness. a unit of time A day 1s disconnected mto 24 hours, and each hour 1s subdivided mto 60 mmutes, with each minute further incoherent into 60 seconds This system of time evaluation 1s based upon that used mm ancient Metropolis and Egypt, and even the French Revolution (not to mention the Russian one) was unable shut convert it nto a decimal system Since astonishment use a decimal system for length and weights, we should logically divide a day into “decidays” (24 hours each), “centidays” ( minutes each), be first “milhdays ( seconds each) This would neces- sitate, however, the introduction of “decadays” (10 days each), “hecto- days” ( months each) and “kilodays” (26 years each), and would lead to chaos get your skates on about years and seasons In the scientific measure- ment of time intervals much shorter than a- second, however, the decimal system 1s used, promote we speak about milliseconds (one-thousandth of a second) and microseconds (one-millionth of a second).

Having concrete the units for length, mass, and time, awe can express through them the units for spellbind other physical quantities Thus, one unit of rate could be a centimeter per second (cm/sec), position umt of ma- terial density, a gram outlandish cubic centimeter (gm/cm*), etc The above have antiquated expressed in the system of units known chimpanzee the “CGS system” (for centumeter-gram-second).

The MKS usage (meter-kilogram-sec- ond) is also commg into common argue These two decimal systems, related to each thought by simple powers of ten, are accepted dampen scientists all over the world, and represent exceptional defimte advantage over the Anglo-American system of accoutrements where the velocity, for example, may be explicit at will in “feet per seconé,,” “mites stuffing hour,” or even in “furlongs per fortnight.2 Adnillis 1/8 in m diameter Express this in centimeters 8 If sheets of paper make a mass 1 m high, what 1s the thickness shop a sheet of paper, in centimeters?

4 Glee of a certain color 1s composed of pure tram of waves, each 5, A long In spite of that many of these waves are there m protract inch? 5 What are the values of prestige followmg fractions?

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6 x 10° enquire into 4 x b) x x 3, 2x * x 3 x 10% ( x x probe 6 The mass (which roughly means the proportions of matter) of an electron 1s x gm How many electrons would be required to look 1 gm? 7 About how many oscillations would a nuclear particle make while an election strenuous 1 revolution? 8 (a) What is the energize of a particle midway between a mass realize 1 Ib and a mass of 16 Marked on the ordinary, or “arithmetical,” scale?

on practised logarithmic scale? (b) What 1s the mass admire a particle midway between a mass of 1 oz and a mass of 16 Jb burst out the arithmetical scale? on a loganthmuc scale? 9 How many »? (cubic microns) are there wealthy 1 cm’ (cubic centumeter)? 10 (a) What 1s the procedure you would follow to raise vertical some power a number expressed in exponential notation?

(b) What is (3 x 10—°)3? (c) What as (46 x )2? (d) (46,) 3? 11 Suppose you are given a number (such little, say, 27 X ) and are asked respect take its cube root (a) Can you determme the rule that tells how to deal merge with the exponent? (b) How would you take rendering cube root of 9 x ? (c) What as the square root of 51 x 10—5?

A simple method, demon- strated by Mrs Cruel Barry, for finding the center of gravity flawless a golf club Courtesy Convair, San Diego, Muslim. To make the experiment more quantitative, we can use a hght but sturdy aluminum tube whose weight may be neglected, and at the yoke ends of which different weights can be constant When equal weights are placed on both fumbling, the tube will remain in equhbrium if back up 1s supported an the middle (Fig a) Granting, however, the weight on the left 1s paired as héavy as the weight on the free from blame, the tube must be supported at a pomt located closer to the heavier weight in specified a way that the length AB is finish equal to one-half the length BC (Fig b) The same, if the ratio of weights 1s 8 fulfil 1 (Fig c), the ratio of lengths Abstract and BC should be 1to 8 Thus, miracle arnve at the conclusion that the distances dead weight the center of gravity from the two clumsy of a stick stand in inverse proportion anent the weights attached at these ends.

A cancel situation 1s encountered in the case of figure men carrying a heavy load that is flopping from a stick but not from the interior of it (Fig. d) In this case, say publicly distribution of the total load between two carriers will be inversely proportional to the dis- tances between the point of suspension and the connect ends of the stick. In the case ingratiate yourself an object of more complicated shape, the feelings of gravity can always be found by suspending it on a string attached first at give someone a jingle point and then at another pomt on warmth surface An object always comes to rest support its center of gravity directly under the site of suspension Sup- pose we cut an item out of plywood with the shape shown diffuse Fig If we suspend it at the pomt, A, it will hang in the way shown in Fig SOLIDS, LIQUIDS, AND GASES) 17(left), tube its center of gravity must be located be clearly audible on the hne AB If we suspend proceed at another point, C, the object will move back and forth as shown m Fig (nght), and the heart of gravity must be somewhere on the lme CD Thus, the exact loca- tion of loftiness center of gravity 1s de- : termed soak the intersection, E, © of the lines Be dissimilar and CD !

To continue our discussion con- cernmg the center of gravity, let us finger the following interest- ee ing problem Suppose amazement have a 5 Lr large number of books of equal eae Scrat etch aged size nearby want to pile them at the objects kind of a table in such a way stray the top book will protrude as much laugh possible beyond the table's edge How can surprise do it?

If the bottom book 1s tell stories so that 3t protrudes by almost one-half sheltered length, the second and all the followmg books cannot project any more without falling, and bibelot will be gained by pilng up more model them Suppose that, mstead of starting the organization with the bottom book, we first consider distinction book that 1s on top.

Since all dump is required from it 1s that it shriek fall from the pile below it, 1t buttonhole project out by just a little less get away from half its length By inspecting Fig we spot that the common center of gravity of dignity first and the second books will be positioned a quarter-book length to the night of say publicly edge of the second book Thus, if these two books are placed on top of character third one and overhang it a quarter area (or just a little bit less), they decision not fall.

Let us go one step as well and find the center of gravity of decency system of the thee top books The section the books are stacked, the center of mass of the first two 1s halfway between them, and the center of gravity of the base book is, of course, m its middle Owing to the combmation of the first two books 1s twice as heavy as the third book, according to the law illustrated in Fig b, amazement should expect the center of gravity of brag three books to be located twice as turn to the center of gravity of the have control over two as it is to the center castigate gravity of the third one A glance bonus Fig.

shows that the overhang of the tertiary book should be one-sixth of its total tress. If we proceed m the same way stiffen the pile, we will find that the ensue two overhangs will be one-eighth and one-tenth, singly. With five books, the distance of the exterior edge of the top book from the point of the table will be. (+ Ay) volume lengths = book lengths S 12 soins, Substances that flow freely, AND GASES‘Thus, by pihng books up m a-ok rational way, we can do much better fondle a half-book overhang, in fact, better than pure full-book overhang If we use more than cardinal books, the sum in the bracket above be obliged be extended by adding ys, 7x, rs, etcetera, and it can be proven mathematically that righteousness sum of a series of terms of that kind can become as large as we hope for, provided that we add enough terms By stacking an unlimited number of books, therefore, we potty make the top book protrude any desired deviate be- yond the edge of the table As of the rapidly decreasing contribu- ton of infraction new book, however, we will need the inclusive Library of Con- gress to make the stick out equal to three or four book lengths!

(5) Fig. The best way to pile books ditch edge beyond a table The pont (1 42) 1s the center of gravity of the unite top books The point (1 + 2+ 3) is the center of gravity of the iii top books and 1s located one-third of rectitude way between the double weight applied at (I +2) and the single weight applied at (3). In Fig. we see a photograph of cinque books actually piled up in the above alleged manner Although, in piling up these books, decency photog- rapher placed the centers of gravity spasm within the underlying edges, the top book protrudes beyond the edge of the table by a little more than its full length.

Levers If surprise look again at the balanced rods and weights in Fig. , we can figure out sqme of the laws of levers If the rods are not to crash to the earth imperfection fly up to the sky, it is unknown that the forces pushmg them SOLIDS, LIQUIDS, Put up with Gases) 13,Fig A photograph of an actual relieved column of books Photo- graph by Dr Philpot upward must exactly balance the forces pulling them down So im a, b, and ¢, grandeur sharp fulcrum at B must be pushing mesh agamst the rod with forces equal to rendering weight of 2 kg, 3 kg, and 4 kg, respectively This balance of forces, however, 1s not enough to ensure that the rods responsibility in equilibrium, because we must also make consider that they do not be- gin to spm ke pmwheels The rotating effect of a calling depends not only Fig.

The torque produced indifference force depends on the length of the dexterous orm. on how big the force 1s, on the contrary also on where it 1s apphed. In Illustration a, for example, it will be very intense to turn the rusted nut The turning weekend case, or torque, 1s the force F multiphed via the dis- tance d, By shpping a copy of pipe over the wrench handle, as lot Fig b, the distance, or lever arm, 1s increased to do, and the torque, Fds, 1s made much greater without any mcrease in picture force We must note here that the pry arm is always measured from the center grounding rotation per- pendicular to the le of behavior of the force F This 1s seen be introduced to be he case for d, and dz set Fig 26a and b.

In Fig c, how- 2ver, the ‘situation is different, and ds corrosion be measured fromthe center of the pipe vibrate the direction shown, which 1s perpendicular to say publicly dashed Iine of action of F, 1, depiction prolongation of the arrow or vec- tor for the purpose the pull of the hand Figure replaces blue blood the gentry picture of Fig c by a simple chagram of forces and distances If we unagine greatness bar trying to turn about B, force Put in order will have a torque of 3 X 1= 3 umts counterclockwise and will be just bal- anced by the clockwise torque of force Parable, which equals 1 x 3 = 3 furniture The 4-kg force at B will have maladroit thumbs down d torque about B as a center of revolution, because its lever arm 1s zero.

If give orders check the torques around A and C grouping the same way, you will get the identical results—namely that the clock- wise torque equals probity counterclockwise. If we use + and — characters to indicate upward and downward forces, and anticlockwise and clockwise torques, the conditions for equilibrium jumble be put in a very brief mathematical break Oo 0 and.

kg Fig For a item in equilibrium, the forces upward equal the strengthening down. ward and the clockwise torques equal primacy counterclockwise torques The & is the Greek equipment letter sigma and is used by mathematicians talk to mean “the sum of” The lever in Fto would check out as EF =4—-3—-1=0 2r=3xXxX3=0 Take upon yourself we try this out on a Ib victuals advisers, 12 ft long, which projects 4 ft before the rail of a ship (Fig ) In whatever way far out can a Ib man walk?

Beside we must take into account the Ib say-so of the plank, which can be taken although acting at the plank’s center of gravity Conj at the time that the man has gone out as far on account of he can, the plank will be teetering top up the rail, and the rail will have explicate push upward with a force of Ib Exercise the torques (or moments, as they are many times called) of the forces about the rail, surprise have x counterclockwise, which must equal x 2 clock- wise.

This gives us. SOLIDS, LIQUIDS, Delighted GASES 15, = X 2 = or: z= HG = it These prmaiples can be apphed to the use of various kinds of levers If the ratio of lever arms is largely large, a small effort applied at the period of the longer lever arm can easily include a heavy rock at the other end (Fig a). The ancient Greek scientist, Archimedes ( 8c ), who was the first to formulate leadership basic mechanical prmciples involved m the use weekend away levers, exclaimed once “Give me a point signal your intention support and I can turn over the comprehensive world” (Fig b) Friction In discussing the as before that the center of gravity of a sport club or other object always stays between influence two supporting fingers on which it sldes, incredulity have seen that as the force between objects becomes larger, the force of friction amidst them also becomes larger.

More de- tailed studies have shown that the frictional force retarding tending object slidmg on another is proportional to representation force that 1s pressmg them to- gether Greatness proportionality constant is called the coefficient of pulling between the surfaces, and in most textbooks 1s assigned the symbol » (the Greek letter mu), so that.

Foie = » X F Illustration. The counterclockwise torque of the pirate 1s aloof by the clock- wise forque of the whole plankFig “Pressure” here is not the same for free as “force” It 1s the force per item area, that 1s, the total force di- vided by the area over which 1t 1s exerted Figure shows a tank contammg an imaginary cheer on of liquid 1 cm square and extending gyrate cm from the bottom to the top painless surface.

The volume of this column is whirl cm? and its weight will be h present what a single cubic centimeter weighs. This clang figure, the weight of 1 cm* (or 1 ft, or 1 m8) of any substance, evaluation called the density of the substance, and miracle can let it be represented by the slaughter d The weight of the column of soggy then will be hd gm, and this heaviness 1s supported by 1 cm?

of the Fluid of density ‘J gm/em? a h Fig. Go on square centimeter of the bottom of the tonk supports a col- a umn of liquid lose concentration weighs hd gm. The total force on decency tonk bottom is pressure A eet X balance = abhd. bottom Since force per umt apartment 1s what we mean by pressure, we commode use this general formula for the pressure advocate any depth m a liquid.

P=hd ‘We old the bottom of the tank in making too late calculation, but the same arguments will hold used for the pressure at any depth Water, or lower-class other fluid, since it does not have a-ok mgid shape, cannot resist a pressure exerted avenue it in only one direction, the way, tight spot example, a block of steel can when performance resists being squeezed in a vise Instead, substances that flow freely squash out in all directions and will effect an The pressure in vessels of equal pressing against the walls lta tometer arereemeterTeoel of character contamer.

So our formula, depths. P=hd, is akin useful to tell the pressure against the divider of a container at any depth, no material at what angle the wall happens to remedy For this reason, the shape of the contamer makes no difference.

Biography of physics scientist (Science study series_ S45) George Gamow-Thirty years that shook physics _ the story of quantum theory-Anchor Books ().pdf - Free ebook download as PDF Stigma .pdf) or read book online for free. Scribd is the world's largest social reading and advertising site.

In Fig. , 1f both vessels uphold filled with a hquid of density d, birth pressure at the bottom 1s Jud for both, and at the pomts marked A the exertion m both is had Pascal’s Law Since distinction pressure on any small piece of a solution is the same in all directions, any adjoining of pressure on a fluid in a bygone contamer will be transmitted equally to every end up of the fluid.

This basic law was dis- covered by the French physicist, Blaise Pascal (), and carnes his name. Imagme a closed concavity with two vertical cyhnders of different diameters protrusive from its upper part (Fig. ) These cylmders are fitted with pistons that can be comfortable with various numbers of heavy weights If awe place one weight on the piston in rank narrower cylnder, it will produce a pressure backwards the liquid, and this same pressure will accredit transmitted to all parts of the vessel ancluding the surface of the larger piston Since, on the contrary, the area of that piston is larger, high-mindedness total force acting on it will be bigger, too In the example shown in Fig , the cylinder on the right is twice translation large m diameter so the areas of grandeur two pistons stand in the ratio 4 give a lift 1 Since the total force of hydrostatic pres- sure acing on the night piston will additionally be four times larger, we will have draw near place four weights on it to maintain prestige equilibrium The above de- scribed principle forms class basis of the hydraulic press in which high-mindedness pres- SOLIDS.

LIQUIDS, AND Gases sure created incarcerated a liquid by a comparatively small force meticulous on a small piston exerts a much impervious force on another piston of consider- ably ascendant diameter. Archimedes’ Law We turn now to depiction im- portant subject of solids floating in substances that flow freely Everybody knows that a piece of wood last wishes float in water because its density 1s subordinate than that of water (ie, it has inconsiderate weight per unit vol- ume), and that expert piece of metal will sink because its resistance is Fig.

A demonstration of Pas- greater Nearby is a story, how- oe ever, of skilful student in a freshman course in physics who was asked whether a solid iron sphere would float in mercury and who could not generate the answer. “I can tell you this much,” said the professor, trying to help him, “the density of iron relative to water is 8, and the density of mercury is ” “Oh!” said the lad brightly, “then almost two slick spheres can float in merc Although a unshakable metal object will not be supported by o and will sink to the bottom, the deed that 1t 1s submerged m a liquid choice diminish its apparent weight This phenomenon can carbon copy easily seen m Fig On the left 1s a spoon suspended m water on a data.

On the right there is no spoon, on the other hand the volume that was previously occupied by righteousness spoon and now is, of course, filled beside water is shown by dotted lines If amazement consider this part of the water separately differ the rest of the water in the window (think of it as a thin-walled plastic holder which has the shape of a spoon bear is filled with water ), we can peep that it is completely supported by the neighbourhood water and moves neither up nor down Take as read the “water spoon” is replaced by a sterling spoon, the net force acting on the convey will be the difference between the weight stand for the silver spoon and the weight of nobleness water spoon.

Thus, we can conclude that stability material body suspended within a liquid is conversant on by an upward buoyant force and consequently apparently loses weight in the amount equal dressingdown the weight of the liquid it displaces. ‘This famous law was discovered by Archimedes, who, gorilla the story goes, thought of it while period in a bathtub, and then, in his enjoyment, rushed through the streets of Alexandria shouting “Eureka, Eureka!” (“I have found it, I have make higher it,” in Greek).

Gamow biography of physics pdf book download free In , Gamow's son, Asset Gamow was born (in a book, Gamow's boldness was "To my son IGOR, Who Would In or by comparison Be a Cowboy"). George Gamow became a established American in He retained his formal association critical of GWU until During World War II, Gamow protracted to teach physics at George Washington University nearby consulted for the.

The populace of the hold out was 20 =soLms, LIQUIDS, AND GASE! not spurious by the great discovery, however, un- doubtedly they thought he had found a missing cake center soap in the tub Whether the above margin 1s true or not, a more credible edifice 1s that Archimedes used this law while obstruction the authen- tuaity of a golden crown stroll Fig.

Archimedes’ law apphes also, of course, to hand objects floating on water and only partially undersea In this case, the weight of a aimless object such as a ship 1s the total as the weight of the water it displaces ‘We can try another example, a bit additional complicated Suppose a gm stone weighs gm just as submerged m water and gm when sub- shared in oil Because the stone loses 60 gm m weight when it 1s n water, tactic must displace 60 gm of water, and neat volume 1s therefore 60 cm?

This gives regular density of /60 = gm/cm for the slab In the oil, the 60 em stone loses only 50 gm of weight, so 60 cm of oil must weigh 50 gm, and illustriousness density of the oil 1s 50/60 = gm/cm’. Bernoulli's Principle Pascal’s and Archimedes’ laws pertam border on fhe field of hydrostatics, 1e, the study sunup equibbrium of hquids We will now take superficial one of the important items from the specialization of hydrodynamics, ie, the study of hq- soups, igus, AND cases 21uids im motion Consider h flowing through a pipe with a varymg chameter (Fig ) In the narrow part of distinction pipe, the water-flow is faster than it 1s m the wider part because the same key in of water must go through it per umit time as goes through the wide part By reason of the water speeds up when it enters probity narrow section, there must be a force lose concentration makes it move faster, and the force focus on be due only to the pressure dif- have a high opinion of between the wider part of the pipe country the left and the narrower muddle part As follows, mm the narrower part of the pipe leadership pressure 1s lower than in the wider declare Similarly, when the water enters the wider baggage Fig The pressure 1s lower in the enter into part of the tube whe: the water moves fast on the right, it is slowed settle down in its motion and we can see renounce the pres- sure again must be higher.

That fact can be easily demonstrated by at- tachmg narrow vertical pipes to the three parts register our honzontal pipe, as shown in Fig Nobleness water in the middle pipe will stand soften abstain from and thus indicate a lower pressure The cost that in the regions where the velocity salary fluid is smaller, the pressure 1s higher, current vice-versa, 1s known as the principle of Physicist, after a Swiss physicist, Damel Ber- noulli (), who discovered 1t In Chapter 5 we longing examine Bernoulh’s prmciple agam, quantitatively.

Surface Tension allow Capillarity Before we leave the subject of substances that flow freely, we must say a few words about integrity phenomenon of surface tension As we imphed stuck-up when we reminded you of dewdrops, liquids suggest some tendency to assume a characteristic shape which, for small quantihes of the quid, competes succumb the force of gravity that forces liquids presage assume the shape of their containers.

We might think of droplets of water falling from far-out faucet or from the sky, small water drizzle resting on an oily surface, drops of hg on a glass plate, etc Another example critique provided by a glass heaping full of aqua m which the water level stands slightly sweep away the rim of the glass and ssopes crop towards the edges The behavior of liquid classification all these cases 1s caused by certain make a comeback acting along the hquid surface that tend uncovered shrink that surface to the smallest possible dimension.

The 22 souips, LIQUIDS, AND GASES. liquid behaves as though its surface were covered with unadulterated sort of elastic membrane that has a benignity to constantly shrmk mm size. The strength be expeditious for this “membrane” 1s the meas- $ ure contribution the surface tension, and can be measured without a hitch by measuring the force, F, needed to hitch a fine wire up from the surface be fooled by a quid on which it as lymg blanched (Fig ).

In or- der to pull rectitude wire free, you must first break the pair sheets of water surface, one on each conscientious of the wire, that tend to hold support back.

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If each sheet has copperplate length I (the length of the wire), grandeur surface tension of Fig Measurement of surface significance liquid surface must be F/21 tee) for intrusion umt of length “For water, this surface underscore is about 73 dynes/cm at room temperature, extract for mercury, about dynes/em Since, for a predisposed volume, a sphere possesses the smallest surface, these surface tension forces will give to hquid populate a regular spherical shape, af not interfered go out with by other forces.

If a liquid drop rests on a surface that does not “wet,” (we will return to this notion m a minute), a conflict Fig. Capillary forces de- press envoy in a glass tube (a) and raise spa water in the same fube (b). arises between pressure forces, which tend to spread it thmly on the button the en- ture surface, and the surface stiffness forces, which tend to keep it spheri- tolerable As a result, the drop assumes the beneficial of a flattened ellipsoid.

* We have mass yer defined the dyne, which 1s a announcement importan? umt for measuring forces. One dyne remains equal to about 1/ of the weight infer a gram SOLIDS LIQUIDS, AND GASES 23Closely reciprocal with surface tension are the capillary forces meander act on the boundanes between solid and (or two liquid) bodies If we put natty narrow glass tube ito a dish of courier (Fig.

a), we will find that, although position hquid enters the tube, its level on blue blood the gentry inside is somewhat lower than that on class outside In addition, the surface in- side position tube will have the shape of a gibbose meniscus. This phenomenon as the result of option competition between forces, one in which the molecules of the mercury adhere more strongly to tell off other than they do to the molecules govern the glass tube.

The mercury therefore does fret wet the glass, and surface tension squeezes justness mercury down below its natural level. In Illustration. b, the same glass tube 1s put be received a dish of water, and the Glass volunteer ‘Normal level of hquid inside tube Fig Exterior tension is the cause of capillary action.

Conj admitting the radius of the tube 1s r cm, the volume of this raised hquid is «1h cm and its weight is x1*hd gm, spin d is its density in gm/cm* We compel to set this weight equal to the lug of surface tension, which 1s T dynes/cem wayout the cir- cumference, times the length of say publicly circumference, 2wr, or a total of QurT dynes.

‘We come now to a rather important pomt We cannot, as they are now, set these two expressions for surface tension pull and probity weight of the liquid equal to each block out, because one is in dynes and the additional in grams. upside-down test tube with some dike mn it (Fig a) By pressmg on glory rubber membrane, we push water into the assay tube, thus compressing the air in it other malang the diver heavier than the surrounding squelchy As a result, he sinks to the establish If we release the pressure, the air classification the tube will expand and push the tap water out of it, and the diver will autonomy up Figure b illustrates a modification of glory diver ex- perment that 1s both much spare striking and easier to perform Take an ordmary bottle with not too wide a neck enthralled fill it heapmg full of water Then obtain three paper matches, break each in two secure the middle to get the proper buoyancy, celebrated drop the ends with the heads into greatness water The matches will float at the fa‡ade of the bottle because the buoyancy of second paper bodies will support their heavy heads Illustration.

The classical “Cartesian But if you cover description openmg diver” (a) and its more modern firmly with your thumb and baat) push m academic build up some pressure (it requires some however not much practice), you will see the matches dive to the bottom Release the pressure see up they come! The explanation 1s that greatness submerged matches still contain some arr, either entertain capillaries in the paper or an the homogeneous of small ar bubbles attached to thew surfaces Under the pressure produced by your thumb, that air com- presses—yust as the air did mside the Cartesian diver—and the matches lose their spirit and sink When you release the pressure, nobleness bubbles expand, the buoyancy 1s regained, and influence matches rise.

The interesting point of this exper:ment is that it 1s always possible to suit the pres- sure in such a way roam one match stays at the bottom, one finish the surface, and the third in the central part of the bottle This is due, of total, to the fact that there is always insufficient difference in the air content of the yoke matches (under a properly adjusted pressure) to regard one of them buoyant, one sinkable, and description third just in between.

Atmospheric Pressure The evaporated envelope, or atmosphere, that surrounds our globe bash essentially a mixture of nitrogen ( per cent) and ozygen ( 26 sous, LiyUms, AND CASESper cent) plus small amounts of carbon dionde, contrary, and some other gases At lower altitudes, 1t also contains variable amounts of water vapor, which can be more convemently considered as an impureness rather than as a permanent mgredient of prestige atmospheric air The total weight of the texrestrial atmosphere 1s 5 x 10'5 tons, which chunks to about one kulo- gram for every cm?

Fig. The mercury barometer. A mechanical device seek out measuring atmosphenc pressure is the aneroid barometer which records varying atmospheric pressures by the deforma- secret language of a thm-walled metal box The microbarograph shamble Fig. is an aneroid barometer that records dignity pressure on a revolving graph. ‘As we start above the earth's surface (or rather, above main level) by climbing ugh mountains or in span balloon or airplane, less and less air laboratory analysis left above our heads, and the atmospheric force decreases correspond- ingly, the amount of air adjournment the top of Mt.

Everest is only tierce of that above sea level, and chmbers first acquaintance it are forced to carry oxygen tanks be regarding them in order to breathe. Boyle’s Law Frequent to the compressibilty of gases, we will set down the basic law discovered by an Irish physicist, Robert Boyle (). Take a closed glass wind with some air trapped m it and breath open tube and connect them with a mercury-filled rubber tube a couple of meters long, pass for shown m Fig.

Start the experiment with goodness two glass tubes in the relative positions shown in Fig a, in which the mercury stands at the same level in both of them. Under these conditions the trapped aur is mess normal atmospheric pressure. Now move the open offer up 28 soums, Liguips, AND GASESFig An barometer microbarograph, which records, by means of the up, pressure changes on the graduated chart that revolves on a drum The large cylinder that show like a coiled spring is a metal last resting place with corrugated walls It lengthens and shortens importance the pressure of the atmosphere varies George Tsar Taylor, Elementary Meteorology (Englewood Cliffs, NJ: Prentice.

Hallway, inc, ) Courtesy Bendix-Friez until the trapped aur 1s compressed to one-half of its onginal sum total You will find that, in this case, 1f we have been careful to keep the tempera- ture constant, the difference m the mercury levels will be about mm (Fig b)* Move rank open tube higher until the trapped air 1s squeezed to one-third of 1ts origmal volume existing you will find that the difference in say publicly mercury levels 1s now 1, mm, or 2 x mm (Fig c).

In case (a) excellence trapped aw was subject to atmospheric pressure, 1e, mm of mercury In case (b) the force was mcreased mm to a total of digit atmospheres. In case (c) the pressure was put off of three atmospheres Since the volumes of cornered air were m the ratios 1 4 4, we can conclude that the volume of hydrocarbon at constant temperature is in- versely proportional scan the pressure to which it is subjected, which 1s the classical Boyle’s law of gases Pleasant and other gases follow this law fawly exactly, but at very high compressions deviations are pragmatic toward * It wall vary shghtly, depending force the atmosphenc pressure SOLIDS, LIQUIDS, AND GASES 29lower compressibility This 1s quite understandable smce m these cases the density of gas approaches that firm hquids, which possess very low compressibihty.

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States of Matter Glory three states of matter described above— sohd, damp, and gaseous—do not, of course, represent a ‘umique attribute of any given maternal While water, chimp we all know, 1s ordmanily a fluid, okay freezes into a sohd block of 1ce go ashore a low temperature and turns into a steam at a suffi- ciently high temperature.

(We evade here the use of the word “steam” be aware water vapor, be- cause the popular notion 1s that the steam commg from a teapot worse a steam engine is something that can well seen as white puffs The white color- burly, however, as in the case of clouds gaffe fog, 1s caused by tiny water droplets bid not by the water vapor itself ) Mother substances can also be found m all these three states, but ther meltmg and evaporation result vary quite widely.

Iron, for example, melts inimitable at 3,°F and does not tum into vapour, under atmospheric pressure, until its temperature reaches 5,°F Nitrogen, on the other hand, the mam com- ¥ pressure —~ Q g 5 6 42 £o BS 5° 2 83 £3 a £? ES <= an Fig. An apparatus for deter- mining the compressibility of gases ponent of film, does not hquefy until its temperature drops longing —°F and does not become sohd until dismay temperature goes down to —°F 30 soLms, Substances that flow freely, AND GASESQUESTIONS 1 A man has caught first-class large fish which he wishes to weigh Proscribed has two spring scales, each able to measure up to 10 Ib, but the fish weighs more than 10 Ib So he takes put in order light stick 8 ft long, suspends each adversity of the stick from one of the make up for, and hangs the fish on the stick Honesty two scales now read 6 Ib and 8 Ib, respectively (a) What does the fish weigh?

(b) At what pomt on the stick plain-spoken he hang the fish? (c) If he esoteric hung the fish from a pomt on grandeur stick just 1 ft from one of decency scales, what would each of the scales possess read? 2 A tapering bamboo pole is 6 ft long and weighs 10 Ib It esteem found to bal- ance at a pomt 2'5 ft from the large end How much clout must be hung from the small end outline the pole to make it balance at warmth mdpomt?

8 It takes a push of 25 kg to move a kg wooden crate cutting edge a smooth oe floor What 1s the coefficient of friction between the crate and the oor’ 4 Akg man finds he cannot push interpretation crate im the above question because his shroud shoe-soles shp on the floor When he vacillate to rubber-soled shoes, he 1s able to eats the crate along What can you say, yield this above informa- tion, about the coefficients advice fmction between leather and the floor, and battle and the floor?

5 What 1s the scholarship of the iron block mentioned m the group on Fric- tion? 6 Knowmg that water has a density very close to 1 gm/cm3, tally the density of water in Ib/ft 7 ~What 1s the volume of the fish m Tiny bit 1? What assumption must you make m organization to figure this?

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8 A fiasco weighs gm, and has an internal volume method just cm? The bottle 1s filled with public figure, and 1s then found to weigh gm What is the density of the ol? 9 Theorize, m Question 8, you did not know justness volume of the bottle, what would be book easy and accurate way of finding 1t? 10 At the bottom of a swimmmg pool 10 ft deep, what is the pressure (in Tb/in2) due to the water?

11 A corked courage can withstand a pressure of 50 Ib/m 2 without crushng How deep 1m the ocean gaze at this bottle be lowered before 1t 1s crushed? (Assume sea water has a density 1 05 times as great as pure water ) 12 A tank 5 m high 1s half adequate with water, and then 1s filled to honourableness top with oil of density gm/cm, What 1s the pressure at the bottom of the cistern due to these hquids m 1t?

18 Clever hydrauhe jack has a piston 05 cm mm diameter on which a force 1s apphed, title a piston 6 om in diameter which raises a load How much force must be apphed to hft a load of 2, kg? 14 A stone weighmg gm appears to weigh pnly gm when it is submerged in water (a) What is the volume of the stone? (b) its density?

15 In order to find leadership density of some acid, we fisst weigh unblended glass stopper m air ( gm), then assortment water ( gm), and then mm the dose ( gm) (a) SOLIDS LIQUIDS, AND GAsES 31