Elementary Expermental Mechanics

An excerpt from the Author's PREFACE:

IN this book an attempt is made to combine theory and practice as closely as possible. Success in teaching is in proportion to the extent to which the active initiative of the student is aroused, and nothing is so effective in this respect as laboratory work, if it be of the right kind. The use of the hand and the eye affords an invaluable stimulus to the imagination and the reason. Without such personal work the interest awakened by a good lecture is apt to be superficial and temporary, and the preparation insured by recitations is too often reluctant and unfruitful. Mechanics is the most fundamental and least attractive part of physics, and in the teaching of it lectures and recitations need all of the aid that laboratory work can supply.

A grasp of principles is of more value to the average student than skill in measurement. While the exercises in this book have been chosen chiefly with a view to the elucidation of principles, the need of an adequate degree of precision in the necessary measurements has been kept in mind. In most cases a test of the accuracy of the work is supplied by a comparison of the results of theory and experiment. The course is not a substitute for, but is preliminary to, a course in the more precise measurement of physical constants. Its aim is to stimulate reflection on concepts and principles, and the value of each exercise is in proportion to the importance and number of the physical ideas which must be considered in performing the exercise. With a few exceptions the exercises have been tried by large classes of students and have been found satisfactory. The exceptions have been carefully tested by myself or an assistant. The introduction of numerous original exercises is due to a lack of suitable familiar experiments. Many well-known exercises have been omitted either because they do not strongly enforce mechanical concepts and principles or because they require complex or expensive instrumental means.

To serve the purpose stated above, each exercise should follow the related lecture or recitation as closely as possible; it will lose much of its value if postponed for several weeks. I have therefore endeavored to choose exercises that call for comparatively simple apparatus, so that sufficient copies of each part may be procured to enable all the students in a class (or section) to work simultaneously and separately on each experiment. (The practice of having two or more students work together is very unsatisfactory.) Important parts of the apparatus serve for a large number of exercises. A few experiments which require apparatus of greater complexity may, if necessary, be omitted or may be performed by the instructor in presence of the class, the calculations being left to the latter.

The statements of theory have of necessity been brief; but brevity in this respect is hardly to be regretted. Diffuseness and repetition are desirable in an oral explanation, but a printed statement can be reread until it is mastered. Diffuseness in a text-book often defeats its own aim. Bright students skip prolix explanations, and others are often only puzzled and confused by what is unessential; statements of principles cannot be predigested by dilution. The directions for the experiments have not been made so full as to leave nothing to exercise the judgment of the student. Condensed formulae for calculation and tabular forms for reporting have not been supplied. These often tempt the student to work blindly and confine his attention to finding figures to fit the formulae and fill the blanks. The instructor may supply such as he thinks necessary either in the lecture which precedes the exercise or on the laboratory blackboard. The topics found under the heading "Discussion" must be regarded as mere suggestions....