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Re: [Phys-L] form of Newtons 2nd law



On 07/26/2012 02:11 PM, Larry Smith wrote:
My engineering colleague says I should teach N2 as F = kma where k
can make it work in non-SI-unit systems. How do you respond to such
requests?

I'm too polite to tell you my first response.

My second response goes like this:

The factor label method basically consists of taking a formula of the
form F = m a and sticking in some various k-factors ... which is always
allowed, because *if you take the units into account* each of the k-factors
is equal to unity.

One of the axioms of arithmetic that you learned in 3rd grade is that you
can always multiply something by unity.

Therefore it is a monumentally bad idea to think in terms of F = k m a.
There is nothing to gain and much to lose by doing so. The alternative
is to understand that units are important, and to understand the axioms
of arithmetic.