> Of [EMAIL PROTECTED] > In USMA 30220 David wrote "you can also use grams-force". > No you can not, not if you use SI. [...] > Use of gram-force is a way to degrade accuracy in measurement and > continues the confusion of mass and weight.
Indeed. The word 'weight' is old and predates our understanding of force and mass. People use 'weight' for both. You can just get in a linguistic and scientific mess if you try to think that 'weight' is never mass. There are people that insist that thrust to weight ratio (used in aviation) is unitless because non-metric units of thrust and weight are both pounds, but one is pounds force and the other is pounds mass. If you point the error out, they will then say that weight is a force, and the argument becomes circular. The SI version is N/kg, of course. Unfortunately the use of 'pound' simply carries the ancient misunderstanding into modern times but we should not let it infect our use of SI. In the past, we have made similar linguistic and scientific misunderstandings with the word 'heat' by using it to refer to temperature or to energy.
