1 Review of Millikan & Gale, PRACTICAL PHYSICS
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 Many of the details are out-of-date, but the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” or “Avogadro’s
law” or “Gay-Lussac’s law” or “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?»