|MadSci Network: Physics|
After years of using the relationship p = m/v, i don't think i ever asked myself "why p?" It's a good question. First i turned to the dictionary. Impetus (Date: 1641) from Latin in- + petere to go to, seek -- from Greek petesthai to fly, piptein to fall, pteron wing Impulse (Date: 1611) from Latin impulsus, from impellere to impel Momentum (Date: 1610) from New Latin, movement Pulse (Date: 14th century) from Latin pulsus, literally, beating, from pellere to drive, push, beat Well, there seems to be a deep common linguistic root here, from the beating pulse of a heart to the beating of a bird's wing. In fact our "push" (Date: 13th century) and "pull" (Date: before 12th century) derive from the Latin pellere. Still, why p? Well, Newton thought of "moments" in a more mathematical, abstract sense in the calculus he was inventing (moments of inertia, for example). In the scientific community at the time Newton published the Principia, *impetus* was the quality of an object that was moving independent of an observed force. Furthermore, the equation p=m/v wasn't given first by Newton, but was developed afterwards. Many scientist/mathematicians developed what we now call "Newtonian Mechanics," and it's easy to imagine some sticking with the old impetus while others used the new momentum. P was a convenient symbol -- m would be confused with mass, i is too often used to indicate an instance of an object. (Mi usually means the mass of the ith object.) To read about the concepts of impetus and momentum, you can read these two essays. http://www.alpha-academic .com/book/chapter2.htm http://www.cor nell-iowa.edu/science_religion/5impetus.html And if this answer isn't satisfying, you can track down Volkmar Schüller at the Max Planck Institute for the History of Science. (No email address, http://www.mpiwg-berlin.mpg.de He has translated Newton's Principia and is preparing a glossary of Newton's technical and scientific terminology. http://www.mpiwg-berlin.mpg.de/resrep9697/ report_96_97.3.html#pgfId=1026049 Cheers, judith bush Judith E. Bush firstname.lastname@example.org The Franklin Institute Science Museum New Media Specialist 222 N. 20th Street 1 (215) 448-1236 Philadelphia, PA 19103-1194 USA AOL IM judielaine
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