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*From*: John Denker <jsd@av8n.com>*Date*: Fri, 14 Sep 2012 11:46:19 -0700

On 09/14/2012 10:24 AM, Larry Smith wrote:

So as to not pick on just Newton's laws _of_motion_, my colleague

would suggest that the k in kma is analogous to the G in Newton's law

of gravity. A former engineering student of his recently e-mailed

back agreeing with the kma and had included a scan from an

engineering textbook where the k appears in the 2nd law. Is anyone

else aware if this is a common practice in engineering? I'd never

heard of it in my physics education.

It's a moving target. Common practice for electrical engineering at MIT

is different from common practice for marine engineering at ITT Technical

Institute. It's also a function of time.

Just now I looked in one of my father's books:

Reno C. King Jr.

_Practical Marine Engineering_

Prentice-Hall (1948)

It is uniformly even uglier than F = k m a. For example, we find on

page 155 the formula

778M(Hs - He)

Thermal horsepower = ---------------

33,000

where M is "the mass or pounds of steam per minute"

Hs is "the heat content in Btu's per pound of steam entering"

He is "the heat content in Btu's per pound of exhaust steam"

In other words, there is no vestige of the idea that physical quantities

have meaning independent of the units in which they are expressed. The

idea of using algebraic methods to keep track of the units is not even

in the same ballpark. Everything is at the arithmetic level, not the

algebra level.

In the chapter on "electricity" on page 268 we find the formula

V × A

KW = ---------

1000

where V is the volts, A is the amps, and KW is the kilowatts.

On the same page we find the diagram

= =

= V =

=_________=

= | =

= A | R =

= =

which expresses Ohm's law and all of its permutations. This is similar

to the "density triangle" that is sometimes taught in lizard-friendly

high-school chemistry classes.

Note that "practical marine engineering" means you are a real blue-collar

_engineer_ i.e. the guy who operates the _engine_ on a ship ... not to be

confused with the quiche-eating white-collar "engineers" who sit in an

office building and scribble on blueprints.

**References**:**Re: [Phys-L] form of Newtons 2nd law***From:*Larry Smith <larry.smith@snow.edu>

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