Essentials of Physics for College Students: a Textbook for Undergraduates and Lecture Course and Reference Work for Teachers and Other Students of Physics. 170 Illustrations

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D. Van Nostrand Company, 1918 - 367 pages
 

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Page 9 - I often say that when you can measure what you are speaking about and express it in numbers you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be.
Page 28 - The total energy of any material system is a quantity which can neither be increased nor diminished by any action between the parts of the system, though it may be transformed into any of the forms of which energy is susceptible.
Page 143 - It is impossible by means of inanimate material agency to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects.
Page 142 - It is impossible for a self-acting machine, unaided by any external agency, to convey heat from one body to another at a higher temperature ; or heat cannot of itself (that is, without compensation) pass from a colder to a warmer body.
Page 29 - If, on the contrary, the forces of the system produce a change of configuration which is resisted by the external agent, the system is said to do work on the external agent, and the energy of the system is diminished by the amount of work which it does. Work, therefore, is a transference of energy from one system to another; the system which gives out energy is said to do work on the system which receives it, and the amount of energy given out by the first system is always exactly equal to that received...
Page 29 - The doctrine of the conservation of energy is the one generalized statement which is to be found consistent with fact, not in one physical science only, but in all. When once apprehended it furnishes to the physical inquirer a principle on which he may hang every known law relating to physical actions, and by which he may be put in the way to discover the relations of such actions in new branches of science.
Page 7 - ... to another, and the constant dissipation of the energy available for producing work, constitutes the whole of physical science, in so far as it has been developed in the dynamical form under the various designations of Astronomy, Electricity, Magnetism, Optics, Theory of the Physical States of Bodies, Thermo-dynamics, and Chemistry.
Page 59 - But a report having been circulated, that some of the gold had been abstracted, and that the deficiency thus caused had been supplied by silver, Hiero was indignant at the fraud, and, unacquainted with the method by which the theft might be detected, requested Archimedes would undertake to give it his attention. Charged with this commission, he by chance went to a bath, and being in the vessel, perceived that, as his body became immersed, the water ran out of the vessel.
Page 3 - To conceive them to move from their places is to conceive a place to move from itself. But as there is nothing to distinguish one portion of time from another except the different events which occur in them. so there is nothing to distinguish one part of space from another except its relation to the place of material bodies. We cannot describe the' time of an event except by some reference to some other event.
Page 209 - Every particle of matter, in the universe, attracts every other particle with a force, which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

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