PHYS114 Lecture Notes - Lecture 1: Carbon-12, Ampere, Kilogram
15 Dec 2015
School
Department
Course
Professor
Document Summary
Cannot be purely derived from other another unit. 7 is the smallest number can"t have a system with less than 7. Second, meter, kilogram, ampere, kelvin, mole: amount of carbon-12 atoms in 12 grams of carbon-12 (avogadro"s number), candela (unit of brightness) From these 7 you can make all of the other units. Unchanging: same today as they are tomorrow: if the base unit changes then all the derived units related to it. Universal: they should be able to measured anywhere and they"ll be will change as well the same. Convenient: should not be that difficult to use/to use well. Sundial (1500bce): as the sun passes through the sky, the shadow on the dial moves and use the shadow to measure time the repeating unit is each day. Water clock (1000ad): attempt to refine the measurement of time water wheel & stream of water filling the buckets. Neither one of these are universal or convenient (and not constant)
