c. commentary
Most textbooks assume that F=ma is an exact relationship, perhaps with the caveat that it is limited by its neglect of special relativity , general relativity , and quantum mechanics. They likewise assume the exact proportionality of (W) to (m) . this assumption of exactness has perhaps made it easier for some authors to go further. and to accept viewpoint #1 above, that F=ma can be used to define force (F) if m and a can be measured accurately. Nevertheless, from the viewpoint of physical law and standards, the accuracy of f=ma first must be determined (which requires independent measurements of F,m,and a) , after which F=ma may (or may not) be employed to define a new standard for force. Currently, if mass is determined by proportionality to weight using a scale balance, then force is indeed the least accurately know of quantities appearing in F=ma , so the proportionality of mass to weight can be employed to obtain a standard for F from accurate measurements of (m) and (a)
c. commentary
Most textbooks assume that F=ma is an exact relationship, perhaps with the caveat that it is limited by its neglect of special relativity , general relativity , and quantum mechanics. They likewise assume the exact proportionality of (W) to (m) . this assumption of exactness has perhaps made it easier for some authors to go further. and to accept viewpoint #1 above, that F=ma can be used to define force (F) if m and a can be measured accurately. Nevertheless, from the viewpoint of physical law and standards, the accuracy of f=ma first must be determined (which requires independent measurements of F,m,and a) , after which F=ma may (or may not) be employed to define a new standard for force. Currently, if mass is determined by proportionality to weight using a scale balance, then force is indeed the least accurately know of quantities appearing in F=ma , so the proportionality of mass to weight can be employed to obtain a standard for F from accurate measurements of (m) and (a)
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