Chpt 1 notes

Chpt 1 notes - Notes on Chapter 1 (pp.1-13) Base Units and...

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John Ellison, UCR p.1 Notes on Chapter 1 (pp.1-13) Base Units and Derived Units Standards are associated with base units , and measurement of a physical quantity takes place by comparison with a standard. We will mostly use SI units (the name comes form the French: Système International d'Unités). The SI system has the base units of meters (m) for length, seconds (s) for time, and kilograms (kg) for mass. See Appendix A in the textbook for a full list of the base units. The SI system is popularly known as the metric system . Derived units are combinations of base units. For example, the unit of power (energy per unit time) is the watt: Other examples of derived units are: Since a wide range of magnitudes of physical quantities are encountered, powers of 10 are commonly used. For example, the prefix k stands for "kilo" and means 1000: This can also be written using scientific notation as The value 0.0032 m would be expressed as 3.2 × 10 -3 m. In order to meet the demands for higher precision, the meter was redefined in 1983 to a derived unit: 1 meter = the distance traveled by light in a vacuum during a time interval of 1/299 792 458 s. The base unit is now the the precisely measured speed of light c : 1 watt 1 W 1 kg m 2 s 3 Conversion of units The SI system is the favored system used by scientists and engineers, but other systems of units are encountered in everyday life. The British system is common in the USA (but no longer in Britain!). Units can easily be converted from one system to another. We use a
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Chpt 1 notes - Notes on Chapter 1 (pp.1-13) Base Units and...

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