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Bell-Ringer!. Without using a measuring device , with 2 partners measure the width of one of the black tables (center of the room). Time: 4 minutes Write your answer on a white board. Why do we have different answers?. Measuring and SI Units. standard. standard.
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Bell-Ringer! • Without using a measuring device, with 2 partners measure the width of one of the black tables (center of the room). • Time: 4 minutes • Write your answer on a white board.
standard standard • Measuring is impossible without the use of a ___________. • A __________ is an exact quantity that people agree to use for comparison. • A measurement must contain 2 parts: • A quantity (number) • A unit (refers you to the specific standard) • What type of standards do we use?
Measuring Systems • English • Developed in Medieval Europe as a combination of Roman and Anglo-Saxon terms • Used in US today • Metric • Developed in 1700s
International System of Units: SI • Uses an improved metric system • Each type of measurement has a base unit.
Length: the distance between 2 points. • Volume: amount of space an object occupies. • Mass: amount of matter in an object. • Time: interval between 2 events
Practical Application: How do we measure the distance to the moon? • In 1970s astronauts placed light reflectors on the moon. • Lasers on Earth aimed at the reflectors and the time it took for the light to go from EarthMoonEarth was recorded. • Compared to the speed of light 3x108m/s. • Distance to moon = 378,000,000 m
Other measurements: • The speed of light is 3x108m/s. This unit is not on the table. • Derived units: obtained by combining units on the table. • Speed (length ∕ time) • Area (length x width) • Volume (length x width x height) • Density (mass/volume)
Temperature • The SI unit of temperature is Kelvin (K). • Most scientific work is measured on the Celsius scale except for work at extreme temperatures. • To convert: 0C + 273 = K