Physics

PHYSICS

  TOWER, SMITH, TURTON,
  AND
  COPE


  [Illustration: (_See p.441_)

  THREE-COLOR PRINTING

  _Y._ Yellow impression; negative made through a blue-violet filter. _R._
  Crimson impression; negative made through a green filter. _RY._ Crimson
  on yellow. _B._ Blue impression; negative made through a red filter.
  _YRB._ Yellow, crimson, and blue combined; the final product. (Courtesy
  of Phototype Engraving Co., Philadelphia.)]


  PHYSICS

  BY

  WILLIS E. TOWER, M. SCI. (Univ. of Illinois)
  HEAD OF THE DEPARTMENT OF PHYSICS, ENGLEWOOD
  HIGH SCHOOL, CHICAGO

  CHARLES H. SMITH, M. E. (Cornell)
  HEAD OF THE DEPARTMENT OF PHYSICS AND ASSISTANT
  PRINCIPAL, HYDE PARK SCHOOL, CHICAGO

  CHARLES M. TURTON, A. M. (Syracuse)
  HEAD OF THE DEPARTMENT OF PHYSICS, BOWEN
  HIGH SCHOOL, CHICAGO

  IN COLLABORATION WITH

  THOMAS D. COPE, Ph.D. (Pennsylvania)
  ASSISTANT PROFESSOR OF PHYSICS, UNIVERSITY
  OF PENNSYLVANIA

  BASED UPON
  PRINCIPLES OF PHYSICS
  BY
  TOWER, SMITH and TURTON

  WITH 7 PLATES AND 448 OTHER ILLUSTRATIONS

  PHILADELPHIA
  P. BLAKISTON'S SON & CO.
  1012 WALNUT STREET


  COPYRIGHT, 1920, BY P. BLAKISTON'S SON & CO.




PREFACE


In the preparation of this text, the _pupil_, his experience, needs, and
interests have been constantly kept in mind. The order of topics,
illustrations, and problems have been selected with the purpose of
leading the _pupil_ into a clear understanding of the physical phenomena
continually taking place about him.

The recommendations and conclusions reached by the "New Movement in the
Teaching of Physics" have been incorporated into the book as a whole.
These conclusions indicate that the most efficient teaching in physics
involves a departure from the quantitative, mathematical methods of
presentation that were in general use a dozen or more years ago, toward
a method better adapted to the capabilities, interests, and requirements
of the young people in our physics classes.

The older methods are effective with a portion of the student body which
has the greater mathematical ability and training, but they discourage a
large majority of the pupils who are not gifted or prepared for severe
mathematical analysis. For this reason, many of the more difficult
mathematical demonstrations often given in physics texts are omitted.
Most of the problems involve only the units employed in practical
every-day measurements.

The portions of Mechanics that are ordinarily so difficult for the
average pupil are not taken up until he has covered considerable ground
with which he is more or less familiar and not until he has become
somewhat accustomed to the methods of study and the technical terms of
the subject.

The pupil comes to the study of physics with a great number of
experiences and impressions of physical phenomena continually occurring
about him. In recognition of this fact, it has been thought best to
consider first the explanation of common things well known to all
pupils, such as the diffusion of gases, evaporation of liquids,
expansion of bodies when heated, and capillary action. Since the
molecular theory of matter is now supported by so many conclusive
evidences, we have not hesitated to make free use of it in the early
chapters. The applications of this theory are extremely helpful in
explaining every-day phenomena. Our experience shows that beginners in
physics understand and apply this theory without difficulty.

The illustrations and drawings have been selected from a pedagogical
rather than a spectacular point of view. Practically all of them are
new. The problems and exercises have been selected for the distinct
purpose of illustrating the principles taught in the text and for their
practical applications.

Many direct applications to common every-day experiences are given in
order to connect the subject matter with the home environment and daily
observation of physical phenomena. Some phenomena are mentioned without
detailed explanation as it is felt that the presentation of these
subjects in this manner is better for this grade of student than a
complete analysis.

Some of the special features of the text may be briefly summarized as
follows:

(A) _Simplicity of presentation_ is emphasized. The methods of attack,
the illustrations and examples employed in developing the subjects are
particularly adapted to beginners in physics.

(B) The text is divided into some _seventy-seven sections_, each
containing material enough for one recitation.

(C) Each of these sections is summarized by a list of _important topics_
which point out to the pupil the principles and subject matter requiring
most careful attention. The lists of important topics are also of
assistance to the teacher in assigning recitations.

(D) The _problems and practical exercises_ emphasize physical principles
as distinguished from mathematical training. A list of exercises is
placed at the end of the several sections.