DOCUMENT RESUME SE 009 208 ED 041 755 Detenbeck, Robert W. AUTHOR Cutts, Fobert M.; TITLE Matter inMotion. Commission on Coil.Physics, CollegePark, Md. INSTITUTION Foundation, Washington,D.C. SPONS AGENCY National Science 65 PUB DATE written for theConference on the NOTE 83p.; Monograph (University New InstructionalMaterials in Physics of Washington,Seattle, 1965) MP-SO.50 HC-$4.25 EDRS PRICE EDRS Price Energy, *College Science,*Conservation (Concept), DESCRIPTORS Experiments, *InstructionalMaterials, Laboratory *Motion, *Physics,Resource Materials ABSTRACT Conference on the This monograph waswritten for the Materials in Physics,held at theUniversity of New Instructicnal intended for collegestudents who Washington in summer,1965. It is professional physicists.The monograph are notpreparing to become inertia for chapters. Chapter1 deals withthe law of contains three Galilean relativityand objects at restand in motion,the theory of law of inertia.The law of momentumconservation deviations from the 2. In chapter3, the applications arediscussed in chapter and its concept of kineticenergy principle of energyconservation and the and problems areincluded in arediscussed. A numberof experiments each chapter. (LC) t. r ! vs- U.S. NIA11101 01 NAIR. EDUCATION i WRFAIN OfFla Of EDUCATION rml nusDOCUMENT HAS KEN INPIODUCE0 EIACIII AS MIRO F1011 TIC PEISON 01 016A11111101101116111ATIN6 11. POWS OF 1111/ 01 OPINIONS CO STAB 10 1101 NECESSARILY 111PRVIII OfFKIAl. OFFICE OF tOUCITION POSITION 01 PRICY. U.I Matter in :Action COMMISSION ON COLLEGE PHYSICS DEPARTMENT OF PHYSICS AND ASTRONOMY UNIVERSITY OF MARYLAND 4321 HARTWICK ROAD COLLEGE PARK, MD. 20740 ROBERT M. COTTS Cornell University ROBERT W. DETENBECK University of Maryland GENERAL PREFACE This monograph was written Icr theConference on the New Instructional Materials in Physics; held at the Universityof Washington in the sum- mer of 1965. The general purposeof the conference was to create effec- tive ways of presenting physics tocollege students who are not pre- paring to become professional physicists.Such an audience might include prospective secondary school physicsteachers, prospective practitioners of other sciences, and those who wishto learn physics as one component of a liberal education. At the Conference some 40 physicistsand 12 filmmakers and design- ers worked for periodsranging from four to nine weeks.The central task, certainly the one in whichmost physicists participated, wasthe writing of monographs. Although there was no consensus on asingle approach, many writers felt that their presentationsought to put more than the customary emphasis on physical insightand synthesis. Moreover, thetreatment was consist of sev- to be "multi-level" that is, each monograph would eral sections arranged inincreasing order of sophistication.Such papers, it was hoped,could be readily introducedinto existing courses or provide thebasis for new kinds of courses. Monographs were written in fourcontent areas: Forces andFields, Quantum Mechanics, Thermaland Statistical Physics, and theStructure and Properties of Matter.Topic selections and generaloutlines were leave authors only loosely coordinatedwithin each area in order to number of free to invent new approaches.In point of fact, however, a monographs do relate to othersin complementary ways, aresult of their authors' close, informalinteraction. Because of stringent timelimitations, few of the monographshave been completed, and none hasbeen extensively rewritten.Indeed, most writers feel that they arebarely more than clean firstdrafts. Yet, is because of the highly experimentalnature of the undertaking, it essential that these manuscriptsbe made available forcareful review by other physicists and for trial use with students. Much effort, therefore, has gone into publishing them in a readable format intended to facilitate serious consideration. So many people have contributed to the project that complete acknowledgement is not possible. The National Science Foundation sup- ported the Confertnco. The staff of the Commission on College Physics, led by E. Leonard Jossem, and that of the University of Washington physics department, led by Ronald Geballe and Ernest M. Henley, car- ried the heavy burden of organization. Walter C. Michels, Lyman G. Parratt, and George M. Volkoff read and criticized manuscripts at a critical stage in the writing. Judith Bregman, Edward Gerjuoy, Ernest M. Henley, and Lawrence Wilets read manuscripts editorially. Martha Ellis and Margery Lang did the technical editing; Ann Widditsch supervised the initial typing and assembled the final drafts. James Grunbaum designed the format and, assisted in Seattle by Roselyn Pape, directed the art preparation. Richard A. Mould has helkld in all phases of readying manuscripts for the printer. Finally, and crucially, Jay F. Wilson, of the D. Van Nostrani Company, served as Managing Editor. For the hard work and steadfast support of all these persons and many others, I am deeply grateful. Edward D. Lambe Chairman, Panel on the New Instructional Materials Commission on College Physics NATTER IN NOTION PREFACE Physics describes the real world. The laws of physics areuseful be- cause they describe the behavior ofactual objects in real situations. We use the language of mathematics to express thelaws, and the logic of mathematics to derive predictions from them. Butphysics is not axiomatic. The assumptions on which physical laws arebased are ex- tracted from the physical world, and the predictionsmade by the laws must be tested in laboratory experiments. This monograph draws upon selected experiences fromlife and from the laboratory to reveal clearly some of the patternsof nature. The conservation laws for linear momentum and for energydevel- oped herein are relevent to all natural phenomena, andprovide insight into a wonderful variety of events. They are notobvious from a super- ficial examination, however, but require carefultraining of the ob- serving eye and analyzing mind to discern them. Wehope that in learn- ing to recognize this order in nature the reader willalso discover some of the beauty we see in herpatterns. From initial observations and experiments we try toformulate general laws which describe many events. Attempts tostate the laws precisely in verbal or mathematical form often lead todefinite ques- tions which must be answered in the laboratorybefore the laws can be stated. Once a law is clearly stated, itshould make definite predic- tions about new situations. These predictions canthemselves be tested in controlled laboratory experiments. Ourconfidence in the general applicability of any law depends ultimately onits past suc- cess in predicting the results ofexperiments. The more times the predictions are confirmed, the more confidently we applythe law to tested. The number and variety of experiments whichconfirm the predic- tions of the laws of momentum and energyconservation is so large that what we can present is limited by taste andtime rather than by any scarcity of data. Within each section of the monographwe have attempted to state clearly the principle to be developed. Thenwe have turned to experi- ment and description to clarify and sharpen he content of the princi- ple. The emphasis has been placed hereupon the general conservation laws and their identical forms in all inertial frames.The princip:a of Galilean relativity has been chosenas the expression of this invar- iance because it seems to us to be the "natural" expression of rela- tivity for elementary mechanics. The monograph is incomplete in that it lacks the sectionon Forces. This section, though necessary to a consistent development, would not have been large (as indicated in the block diagram of the monograph below). We hope that with a thorough understanding of these two conservation laws, together with an introduction to the study of interactions through forces and potential energies, the studentcan study further the interactions of matter in context. We hope he will use the tools of the conservation laws to study the structure of mat- ter, the collisions of elementary particles, the nature of fields, etc., in other parts of his course. We have assumed that the student is familiar with the vector, de- scription of motions before he reads this monograph. A suitable back- ground might be found in the first six chapters of the PSSC text ,ysics, or the monograph Motion written by Gerhart and Nussbaum at the same time as this one. The original vision of the monograph on momentum and energycon- servation looked something like the sketch below, in which the size of each area is roughly proportional to the number of pages. Proposed Law of Inertia . Momentum Conservation Forces energy Conservation As it turned out, the monograph is not completed. The completed sections are indicated below to roughly the same scale as above. Done Missing - LAW OF INERTIA Galilean relativity MOMENTUM CONSERVATION 0---Forces ENERGY CONSERVATION (Kinetic) Potential energies' thermal energies, etc. The "Law of Inertia" and "Conservation of Momentum" chapters are sufficiently complete that they can probably be used in the classroom. Although some "thinking" questions are presented in the text, addi- tional drill problems will be needed for classroom use. Even a casual reading of the text will make it clear that it is intended to be used a.,ng with classroom demonstrations as well as laboratory experiments. --1 IMMEMIMMEMMEMMOW CONTENTS 1 THE LAW OF INERTIA 1.1 Introduction 1 1.2 Law of inertia for objects at rest 1 1.3 Law