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Copyright © 2007 jsd

1  Review of Millikan & Gale, PRACTICAL PHYSICS

Title:PRACTICAL PHYSICS
Author:Robert Andrews Millikan
Author:Henry Gordon Gale
in collaboration with:Willard R. Pyle
Copyright:1922
URL:https://www.archive.org/details/practicalphysics00millrich

This book is fun to read. It gives many examples of practical applications of physics, and has some class and panache ... but some of the facts are wrong. Many of the details are out-of-date, but the underlying principles are timeless. If nothing else, it may serve as a valuable trove of diagrams. Everything is freely re-usable, since copyright is long since expired.

1.    (+) On page 17:  In the section on Pascal’s law, it gives practical examples such as a hydraulic press, hydraulic elevators.

2.    (+) On page 19:  It applies Pascal’s principle to the example of firefighting, i.e. why you want your water reservoir to be higher than the tallest building in town ... which seems nice and practical to me.

3.    (+) On page 22:  It mentions submarines as an example of buoyancy.

4.    (+) On page 27:  It shows a 1-gallon metal can crushed by atmospheric pressure, which is always a fun demo.

5.    (+) On page 28:  In connection with water pumps, it quotes Galileo as saying evidently “nature’s horror of a vacuum did not extend beyond 32 feet”. That’s amusing. I’d never heard that quote before.

6.    (+) On page 32:  Diagram of mercury diffusion pump. Very practical, but too complicated for ordinary pedagogical purposes.

7.    (–) On page 37:  It gives the pressure versus height in the atmosphere as an example of “Boyle’s law”. Alas, the example they give is just plain wrong. This is the eleventeenth example of why I recommend teaching the ideal gas law, and consider it a big mistake to teach the “simplified” laws such as “Boyle’s law” and “Charles’s law”. The “simplified” laws practically beg the students to make OTBE errors, even if the text is correct in some narrow hyper-technical sense ... and things only get worse when the text is wrong. See www.av8n.com/physics/gas-laws.htm especially www.av8n.com/physics/gas-laws.htm#sec-otbe and see also item 24.

8.    (–) On page 39:  The atmosphere-related questions are loaded with multiple misconceptions.

9.    (+) On page 43:  In the section on buoyancy and Archimedes’s principle, it gives examples such as Cartesian divers.

10.    (–) On page 66:  There is a series of bogus questions about the forces on kites and airplanes. See also item 11.

11.    (–) On page 78–80:  The discussion of aircraft stability is wildly unrealistic.

12.    (+) On page 45:  Diving bell.

13.    (+) On page 46:  Diving suit.

14.    (–) On page 73:  The story about Galileo and the leaning tower is not nowadays considered true.

15.    (+) On page 84:  Centrifugal cream separator.

16.    (+) On page 85:  Newton’s cradle. This is a great demo, often not emphasized enough these days. It illustrates the flow of momentum, and flow of energy.

17.    (+) On page 87:  Loop-de-loop. Cute illustration of basic principles.

18.    (+/–) On page 88:  A hydraulic ram is used to raise water above the level of the source. Very practical. Left as an exercise; may be difficult for typical students. The most-important application i.e. broken pipes (water hammer) not mentioned.

19.    (+) On page 95:  It says «minute floating particles of all liquids are quite accurately spherical». (That’s something Millikan knows about.)

20.    (+) On page 100:  Needles and insects supported by surface tension.

21.    (+) On page 109:  Compound pulleys. Very practical.

22.    (+) On page 117-119:  Lots of nice practical mechanisms: Capstan, crew jack, train of gears, worm gear, differential pulley.

23.    (–) On page 121:  The crane mechanism is oversimplified. What determines the angle of the boom?

24.    (–) On page 136:  It mentions Charles’s law and Gay-Lussac’s laws without adequately specifying their limits of validity and their relationship to the general ideal gas law. This can be expected to produce OTBE errors. See item 7.

25.    (+) On page 139:  It points out that only the top of a lake freezes in winter, and this is important for aquatic life. A nice connection between a physical property and a practical consequence.

26.    (+/–) On page 140:  Ball and ring for demonstration of thermal expansion. This deserves more emphasis than it receives, because students often have misconceptions about what happens when the ring is heated. The physics can be expressed as a scaling law.

27.    (+) On page 143:  Bimetallic strips as temperature transducers.

28.    (+/–) On page 146:  Shows diagrams of bearings, including double-cone bearings suitable for handling side loads. Alas it doesn’t explain the connection between structure and function.

29.    (+) On page 462:  «In what direction must a fish look in order to see the setting sun?»
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Copyright © 2007 jsd