standards-of-measurement-1220585633762882-8.ppt

7/25/2019 standards-of-measurement-1220585633762882-8.ppt

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Standards of Measurement

The International System of

Units(SI)


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Units and Standards

In order for a measurement to beuseful, a measurement standard

must be used. A standardis an exact quantity that

people aree to use for comparison.


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Measurement Systems

Suppose the lenth ofa strin in a ball ofyarn is !"". #an you

tell ho$ much strin isin the ball%

&' It could be !" feet, !" meters,or some unit you*+e ne+erheard of. In order for a measurement to

mae sense it must ha+e a numberand a unit.


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International System ofUnits

In the U.S. $e buy mil by the allon,potatoes by the pound, and lumber bythe foot.

These are a part of the -nlish systemof measurement.

Most other nations use a system of

measurement based on multiples of ten. This is no$n as the International

System of Units orSI.


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#ommon SI re/xesPrefx Symbol Multiplying Factor

0ilo1 !"""

2eci1 d ".!

#enti1 c "."!

Milli1 m ".""!

Micro1 m "."""""!

&ano1 n ".""""""""!


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SI 3ase Units

QuantityMeasured

Unit Symbol

4enth Meter m

Mass 0iloram

Time Second s

-lectric current Ampere A

Temperature 0el+in 0

Amount ofsubstance

Mole mol

Intensity of liht #andela cd


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4enth

The SI base unit for lenth is the meter(m).

5emember6 SI is based on po$ers of ten

Therefore6!m7!"dm7!""cm7!"""mm

Metric rulers and meter stics are used tomeasure lenth.


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#hoosin a Unit

The si8e of the unit you use tomeasure $ith $ill depend on the si8eof the item bein measured.

! meter !centimet

er

!" football/elds7 !ilometer


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9olume

The amount of space occupied by anob:ect.

9olume7 lenth x $idth x heiht

97 ;cm x ;cm x;cm

97


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Mass

Measurement of the matter in an ob:ect. 3ase unit6 ilorams ()

>rams () and millirams (m) are usedfor measurin ob:ects of small mass.

?hich ballhas moremass%

@o$manyramsareinone,ilora

m%


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Summary A standardis an exact quantity that people aree to use for

comparison.

In order for a measurement to mae sense it must ha+e a numberand a unit.

The International System of Units orSIis a system of measurementbased on units of !" and used by most nations around the $orld.

-+ery type of quantity measured in SI has a base unit and a symbolfor that unit.

The SI base unit for lenth is the meter (m).

The si8e of the unit you use to measure $ith $ill depend on the si8eof the item bein measured.

9olume7 lenth x $idth x heiht

Mass is the measurement of the matter in an ob:ect ().

2ensity is the mass per unit of +olume of a material. (-xpressed asrams per cubic cm)

The SI unit for time is the second (s).

The SI unit for temperature is the 0el+in (0).

standards-of-measurement-1220585633762882-8.ppt

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