Standards of Measurement Chapter 1 Section 2

Units and Standards Standard-an exact quantity that is agreed upon to use for comparison hands feet piece of string

Measurement Systems English inch pound ounce Metric centimeter gram liter

Fundamental Units There are 7 fundamental units. All other units are a combination of these units. kilogram meter second kelvin candela mole ampere

Derived Units A unit that is a combination of fundamental units Newton-measurement of force combination of kg, m, and s-kg. m/s 2 Joule-measurement of energy combination of kg, m, and s-kg. m 2 /s 2

International System of Units SI – 1960 renamed the metric system to SI to indicate an improved version standard system of measurement used worldwide prefixes based on powers of 10

SI Prefixes Kilo-k-1000 Centi-c-0.01 Milli-m Convert 23 km to mm Convert 75 g to kg

Measuring Distance Length (distance) l (d) distance between points units of meter, centimeter, or kilometer Appropriate use of units

Meter, m 1 st defined at 1/10,000,000 the distance from north pole to equator pass through Lyons, France 1983 light traveling in a vacuum for 1/299,792,458 s

Measuring Matter Mass amount of matter in an object units are kilogram

Kilogram, kg Mass of small platinum-iridium metal cylinder Not reproducible with natural occurrence

Measuring Time Time interval between two events unit is second

Second, s First defined as 1/86,400 of a solar day Universe is expanding and Earth’s rotation is slowing down so time was not constant 1960’s atomic clocks developed Now so many vibrations of Cs-133 atom

Measuring Temperature Temperature the measure of the hotness or coldness units are Celsius or Kelvin

Kelvin, K Originally Cesius based on the boiling and freezing points of water Now based on the triple point of water. Triple point is when all three phases of water are present