From: Joseph B. Reid <[EMAIL PROTECTED]> To: U.S. Metric Association <[EMAIL PROTECTED]> Date: February 27, 2001 16:55 >John Tauxe wrote in USMA 11327: > >>Well, my note about not being able to measure mass generated some >>discussion, alsmost all of it identifying the balance as a way of measuring >>mass. I still disagree. >> >>At 13:11 2001-02-27 -0600, Gene Mechtly wrote: >>>On Mon, 26 Feb 2001, John Tauxe wrote: > >>Show me a device that can measure mass under zero gravity and I'll admit >>that mass can be measured. >> >>- John >> >>_____________________________________________________________ >>John Tauxe, PhD, PE voice: 505.662.0707 ext 15 >>Neptune and Company fax: 505.662.0500 >>1505 15th St. Suite B mailto:[EMAIL PROTECTED] >>Los Alamos, NM 87544-3063 LANL mailstop M969 >>___________ http://www.neptuneandco.com/~jtauxe _____________ > > >Our standard of mass is the master Kilogram, which is preserved with all >precautions. It was constructed to have the mass of one decimetre cubed >atwater at 4°C. All other kilogram standards have been prepared by >comparison with the master (or prototype) Kilogram. The comparison could >theoretically be made anywhere: at sea level, on Mount Everest, on the >moon. You are right that the weights of the two standards are being >compared, but if the weights on the balance are equal, then the masses are >equal, even though the ratio between mass and weight depends on the local >acceleration due to gravity. The mass of an object is constant, the weight >varies with location. > >Under zero gravity the only test of mass would be the measurement of the >acceleration produced by a standard force, a most difficult procedure. It >also raises the problem of standardizing the force. > >I think you suffer from the engineering tradition of considering the >pound-force as a basic unit. a la Donald Shead! Duncan An engineer wrote to the Globe and Mail that >in going metric Canada was changing from using a system based on weight to >one based on mass. He admitted that he would expect to get more butter in >a pound in Denver than he would in Toronto, although the difference would >be negible. > >Joseph B. Reid >17 Glebe Road West >Toronto M5P 1C8 Tel. 416 486-6071 >
