Stan, In Classical Mechanics, position, speed, and acceleration *must* be with respect to a particular "frame of reference"; that is, with respect to a particular "coordinate system" if position, speed, acceleration, *and weight* are to be measured without ambiguity. There must be an origin, and definitions of three coordinates (rectangular, cylindrical, spherical, or three coordinates from some other of more than ten sets) for locating positions in space.
Classically (no speeds of physical objects approaching c, the speed of light), mass is independent of position, speed, and acceleration. In this case, one may write force = mass times acceleration, Newton's Second Law in its most simple form. However, weight (defined in SI as mass x acceleration of gravity) *requires* either specification or unambiguous knowledge of the particular frame of reference in question. This necessary requirement for a "frame of reference" is *missing* in your discussion of mass and weight. A useful illustration of weight variations with respect to different "frames of reference" is the fact that an earth orbiting astronaut is nearly weightless in the reference frame of the spacecraft, but is not weightless in the frame having its origin at the center of the earth. The weight of the astronaut is reduced by only a small amount when in near earth orbit wrt the earth. A larger reduction to about 1/6 the value on earth wrt the earth arises in close orbit around the moon or on the surface of the moon in the frame with its origin at the center of the moon. Gene Mechtly. ---- Original message ---- >Date: Thu, 30 Aug 2007 08:16:48 -0400 >From: "Stan Jakuba" <[EMAIL PROTECTED]> >Subject: [USMA:39292] Re: Current version of PCI list >To: "U.S. Metric Association" <[email protected]> >... > >Attached please find the subject coverage as it is presented in my book >(pages 24 thru >31 if you have it). >
