b'\x1b\x1a\x19 \x1f\x18\x1d\x17\x16Metric MattersHERTZ, NEWTON AND PASCALBy Edmund IsakovS I-derived units of measurementThis is the fourth in a series of articles about the metric system.aredefinedalgebraicallyin terms of base units. There are 22 SI-derived units. Units of measurementpression of the hertz in terms of SIHelmholtz said, One should em-related to geometry, lighting, radia- base units is 1s or s -1 . phasize the extraordinary import of tion and chemistry are not includedHeinrich Hertz (1857-1894) wasHertzs discoveries in relation to our in this series. a German physicist. He found thatwhole concept of nature.On Oct. 20, 1960, the 11th meet- electrical conductors reflect wavesOn Oct. 21, 1948, the ninth CGPM ing of the General Conference onand concave reflectors can focusadopted the newton as a unit of Weights and Measures, also knownthem. These waves, originally calledforce. A force of 1 N accelerates a as CGPM, adopted the hertz as aHertzian waves and now knownmass of 1 kg at a rate of 1 m per sec-unit of frequency, replacing the pre- merely as waves, come in the formond per second (ms 2 ). The math-vious name for the unit, cycles perof both light and radio waves. ematical expression of the newton second. Hertz replaced cycles perThe unit of hertz bears his name.is N = kgms 2 . Expression of the second in common use by 1970. Ex- Austrian physicist Hermann vonnewton in terms of SI base units is Economical High Feed MillingThe versatile Pramet ISSN11 milling cutters are suitable for high feed copy milling, helical interpolation, ramping and face milling in die & mold and general machining industries.SNGX11 inserts offer a strong cutting edge with eight indexes, cutting up to .067 in depth for price-per-edge efficiency.When you add a Pramet product to your shop,SNGX11 MM Inserts SNGX11 M Insertsyou add our entire team including quality productionMM geometryDouble-sided facilities, reliable delivery andfor smoothersquare inserts with nationwide support. To learncut eight cutting edges more go towww.dormerpramet.com MM geometry for stainless steels, softM geometry for steels and cast steelsand cast steels and superalloysWe proudly manufacture your team of brands24JULY 2020 MetricMatters.indd 24 6/16/20 9:22 PM'