On Thu, 25 Sep 2003 11:51:47 -0700, Jim Kelley
wrote:

"Fundamentals of Physics", Haliday and Resnick, Second Edition, 1981

Appendix F, Conversion Factors

Mass

"Quantities in the colored areas [ounce, pound, ton] are not mass units
but are often used as such. When we write, for example 1 kg "=" 2.205
lb this means that a kilogram is a _mass_ that _weighs_ 2.205 pounds
under standard condition of gravity (g = 9.80665 m/s^2)."

The units dyne, Newton, pound, and poundal are listed elsewhere in
Appendix F as units of force.

73, AC6XG

Apparently Halliday and Resnick were a lot smarter a couple of decades
earlier, when they were only a little past their prime:

Robert Resnick and David Halliday, Physics For Students of Science and
Engineering, John Wiley & Sons, 1960.

[page 10]

Legally, the pound is a unit of mass. But in engineering
practice the pound is treated as a unit of force or weight.
This has given rise to the terms pound-mass and pound-
force. The pound mass is a body of mass 0.45359237
kg; no standard block of metal is preserved as the pound-
mass, but like the yard it is defined in terms of the mks
standard. The pound-force is the force that gives a
standard pound an acceleration equal to the standard
acceleration of gravity, 32.1740 ft/sec².

So what are you going to believe? The main text of a book which
actually uses pounds? Or something hidden away in an appendix (which
the authors likely assinged some secretary to put together for them),
in a book which doesn't even use pounds?

Now go back in the book you have, and take a look at some of the
earlier stuff in it.

[page 356]

In the engineering system the unit of heat is the
British thermal unit (Btu), which is defined as the
heat necessary to raise the temperature of one
pound of water from 63 to 64°F.

How much water? You don't think that this is the amount of water that
exerts a certain amount of force due to gravity, do you?

What about when they give specific heat capacity in units expressed in
as Btu/lb °F in this book? What the hell do you suppose those units
in the denominator are? The corresponding metric unit in their book
are "cal/g°C"; does that give you any clues?

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/