# 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.

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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

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? standard standard

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 EarthMoonEarth 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 = K

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