(is,. A FIRST COURS] PHYSICS BY ROBERT ANDREWS MILLIKAN, Pu PROFESSOR OF PHYSIOS IN THE UNIVERSITY OF < AND HENRY GORDON GALE, PhJ ASSOCIATE PROFESSOR OF PHYSICS IN THE CJNIVERSIT REVISED EDITION KNTLKLH AT M'AI IOM S>‘ U \ (*oi*v limit, nxt(>, in UOBKKT A. Ml I,UKAN v\t» HI \ U\ all hwmt.s him in i n hllM* PEEFACE The chief aim of the first edition of this bool elementary physics in such a way as to stimulate some thinking on his own account about the ho\ the physical world in which he lives. With this abandoned the formal, didactic method so large the preceding decade. In place of it we used t uniformly started with some simple experimen known phenomenon. The consideration of he pened was then followed by a discussion of w definitions being in general inserted only aft< them had been felt by the pupil. Finally, a c set of questions and problems following each da than each chapter, led the student to find for hin: tions between the phenomenon in hand and otb penings. Such a* method led inevitably to the of the apparently disconnected facts of physic great underlying principles, such as the kim PREFAC iv and of electricity would be precisel sunset as merely observable facts their interpretation in the light of In the present revision our forn tained. In addition, we have aimed thoroughly up to date, and to im seemed desirable. The most impo as follows: (1) The approach to the subjecl more simple and more interesting on force and motion until after t nating phenomena of liquids and (2) The treatment of force and ably simplified. (3) The book has been shorten* order to give opportunity for an exi the course. (4) A carefully selected list of : lems has been inserted at the end. (5) The absolute units have bee than in the first edition; for examj are defined in this edition in terms c TTip •nrAQPrvfafinn rvf fUo •fnn PREFACE (10) The portraits of some of the most emit physicists have been inserted, as well as thos pioneers of the science. The frontispiece illustrates the combinatio: applied physics, which is the guiding principle For the sake of indicating in what directions be made if necessary, without interfering w paragraphs here and there have been thrown These paragraphs will be easily distinguished room experiments, which are in the same type the most part descriptions of physical appliano Some teachers prefer to have the chapter ference (X) follow immediately after the cl mometry and expansion (VII). This order is to the authors as that given. It is quite impossible for us to make suita of the assistance which has been derived frc which have been sent to us from all over the We owe an especial debt, however, to H. Clyd Milwaukee; Willard R. Pyle, of New York ; "V and Edwin S. Bishop, of Chicago. The University of Chicago K. H. CONTENTS CHAPTER I. MEASUREMENT... Fundamental Units. Density II. PRESSURE IN LIQUIDS. Liquid Pressure beneath a Free Surface. Pas Principle of Archimedes III. PRESSURE IN AIR. Barometric Phenomena. Compressibility anc of Air. Pneumatic Appliances 1% MOLECULAR MOTIONS. Kinetic Theory of Gases. Molecular Motic Properties of Vapors. Hygrometry. Molece Solids V. FORCE AND MOTION. Definition and Measurement of Force. Compos lution of Forces. Gravitation. Falling Bodies. VI. MOLECULAR FORCES. Elasticity. Capillary Phenomena. Absorptioj X LIST OF ILLUSTR 31. Henry A. Howland. 32. Sir William Crookes. 33. Christian Huygens. 34. Arthur L. Foley’s Sound-Wave Photograj 35. Three-Color Printing. 36. Cinematograph Film of a Bullet fired thr< 37. Joseph John Thomson. 38. William Conrad Rontgen. 39. Antoine Henri Becquerel. 40. Madame Curie. 41. E. Rutherford. A FIRST COURST PHYSICS CHAPTER I MEASUREMENT Fundamental Units 1. Introductory. A certain amount of k familiar things comes to us all very early ii almost unconsciously, for example, that sto] loons rise, that the teakettle stops boiling from the fire, that telephone messages travel rents, etc. The aim of physics is to set us t how and why such things happen, and to . acquaint us with other happenings which v noticed or heard of previously. Most of our 2 MEASUREMENT first problem in physics is then to 1< the units in terms of which all our ] expressed. 2. The historic standard of length nations have at some time employed name of which bore the same signifi English. There can scarcely be any d( each country this unit has been derivi the human foot. It is probable that in 1 (a unit which is supposed to have r of the arm of King Henry I) became < ard, the foot was arbitrarily chosen standard yard. In view of such an orig no agreement existed among the uni countries. 3. Relations between different units been true, in general, that in a given units of length in common use, such inch, the hand, the foot, the fathom, t have been derived either from the lem bers of the human body or from equ tudes, and in consequence have beer FUNDAMENTAL UNITS 5. Origin of the metric system. At the tim Revolution the extreme inconvenience of exist measures, together with the confusion arising different standards in different localities, le Assembly of France to appoint a commission t logical system. The result of the labors of 1 was the present metric system, which was intro< in 1793, and has since been adopted by the most civilized nations except those of Great United States; and even in these countries its work is practically universal. 6. The standard meter. The standard leng\ system is called the meter . It is the distance, temperature, between two transverse parallel lines ruled on a bar of platinum- iridium (Fig. 1), which is kept at the International Bureau of Weights and Measures at Sevres, near Paris. In order that this standard length might be reproduced if lost, the com¬ mission attempted to make it one ten- millionth of the distance from the 4 MEASUREME 7. Metric standard capacity. The is called the liter. It is the volume of of a meter (about 4 inches) on a side, 1000 cubic centimeters (ce.). It is e< A liter and a quart are therefore, rout. 8. The metric standard of mass, connection between the unit of long the commission directed a committee to prepare a cylinder of platinum \vh weight as a liter of water at. its tempo] namely, 4° Centigrade (40° Kahrenhe of this cylinder made of platinum-irf with the standard meter, now roprost in the metric system. If is (allied th is equivalent to about 2.2 pounds. () mass was adopted as the fundament named the t/ram. For practical pur} uiat/ he taken ax etjual to the maxx o f on< 9. The other metric units. The th metric, system ■tint meter, the lito decimal multiples and submultiplej> length, volume, or mass is eoniteeh FUNDAMENTAL UNITS • 10. Relations between the English and met following table gives the relation between the English and metric units. 1 inch (in.) = 2.54 cm. 1 cm. = .39 1 foot (ft.) = 30.48 cm. lm. =1.0 1 mile (mi.) = 1.609 km. 1 km. = .62 1 sq. in. = 6.45 sq. cm. 1 sq. cm. = .15 1 sq. ft. = 929.03 sq. cm. Isq. m. =1.1 1 cu. in. = 16.387 cc. 1 cc. = .06 1 cu. ft. = 28,317 cc. 1 cu. m. =1.3 1 qt. = .9463 1. 11. =1.0 1 grain = 64.8 mg. 1 g. = 15. 1 oz. av. = 28.35 g. 1 g. = .03 1 lb. av. = .4536 kg. 1 kg. = 2.2 This table is inserted chiefly for reference tions 1 in. = 2.54 cm., 1 m. = 39.37 in., 1 kilo 1 km. = .62 mi., should be memorized. Portion* and of an inch scale are shown together in Fi£ centimeter 0 1 2 3 4 5 6 Now il is found that just volume e.an be red need to me termination of any measurable in a steam boiler, the. velocity of electricity consumed by ai magnetism in a magnet, etc., < urements of length, mass, ai the and the seeond are < units. Whenever any measur equivalent in terms of eon tin said, for short, to be express* Second) units. 13. Measurement of lengtf body (consists simply in comp: standard meter bar kept at the that this may be done con von the same length as this stain and scattered all over the wor sticks. They are. divided into groat care being taken to ha same length. The method of r a bar is more or less familiar 14. Measurement of mass. FUNDAMENTAL UNITS as many of the standard masses as are requi pointer back to 0 again. The mass of the l the sum of these standard masses. This is correct method of making a weighing, and is called the method of substitution . If a balance is well con- / 1 structed, however, a weighing I 1 may usually be made with suffi- / 1 cient accuracy by simply plac- I \ ing the unknown body upon / 1 £ one pan and finding the sum s a ) of the standard masses which Fig 3 Tbe must then be placed upon the other pan to bring the pointer again to 0. T method of weighing. It gives correct results when the knife-edge C is exactly midway bet of support m and n of the two pans. The met tion, on the other hand, is independent of the knife-edge. QUESTIONS AND PROBLEMS 8 MEASE 1< I)KN! 15. Definition of density. \Y substances, such as lead, wood, manner described abov(\ they a; ent masses. The. term ff densit of unit volume of a substance. Thus, for example, in the Ei the unit of volume, and the poun< foot of water is found to weigh ( English system the densit i/ of tea In the CUES. syst(*m the on unit of volume, and the grain a." say that in this system the dt cubic centimeter, for it will be i taken as the. mass of 1 cubic otherwise expressly st...
Amiga789