# THE SI system and units of measurement - PowerPoint PPT Presentation

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## THE SI system and units of measurement

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### Units of Measurement Measurement is used to measure quantities. Quantity is something that has magnitude, size, or amount (volume). A quantity is not the same as a ... – PowerPoint PPT presentation

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Title: THE SI system and units of measurement

1
THE SI system and units of measurement
• Units of Measurement

2
Measurement
• Measurement is used to measure quantities.
• Quantity is something that has magnitude, size,
or amount (volume).
• A quantity is not the same as a measurement.

3
SI system of measurement
• In the late 18th century, scientists used the
metric system. The metric system is a forerunner
to the SI System.
• Scientists all over the world use a single
measurement system called Le Systeme
International dUnits, abbreviated SI.
• It was adopted in 1960 and has both base units
and derived units.

4
SI Base units
• The most common base units that we will study
include

Quantity Quantity Symbol Unit name Unit abbreviation
Length l meter m
Mass m kilogram kg
Time t second s
Temperature T Kelvin K
5
Length
• The SI standard unit for length is the meter.
• A distance of 1m is about the width of an average
doorway.
• To express longer distances, the kilometer (km)
is used. One kilometer is equal to 1000 m.
• To express shorter distances, the centimeter (cm)
is used. One centimeter is equal to 1/100 of a
meter.
• Length can be measured using a meter stick or
rulers.

6
Mass
• Mass is a measure of the quantity of matter. The
standard unit for mass is the kilogram (kg).
• The gram (g), which is 1/1000 of a kg is used for
measuring masses of small objects such as flasks
and beakers. Mass is typically measured using a
balance.
• Mass is different from weight. Weight is a
measure of the gravitational pull on matter. The
weight of an object increases as gravity acts on
it. The weight of an object on the moon is about
1/6th of its weight on Earth. So, a human on
Earth who weighed 126 lbs. would weight how much
on the moon?

7
Time
• The standard unit of measurement for time is the
second (s).
• Time can be measured using stop watches, clocks,
count down timers, and other time pieces.
• Larger amounts of time are measured in minutes
and hours.
• There are 60 seconds in one minute. There are 60
minutes in one hour. Given that there are 24
hours in one day, how many seconds are there in
one day?

8
Temperature
• The standard unit of measurement for temperature
is degrees Kelvin (K).
• Temperature can also be measured in degrees
Celsius (C) and degrees Fahrenheit (F).
• To convert degrees Celsius (C) to degrees
Fahrenheit (F) multiply by 1.8 and then add 32.
To convert degrees Fahrenheit to degrees Celsius,
subtract 32 and then divide by 1.8
• K C 273
• Temperature is measured using a thermometer.
(measures the degree of heat or coolness)

9
Derived units
• Derived units are combinations of base units.
They are produced by multiplying or dividing
standard units. The derived units we will study
include

Quantity Quantity symbol Unit Unit abbreviation
Area A square meter m2
Volume V cubic meter m3
Density D kilograms per cubic meter kg/m3
10
Area
• Area is length times the width. It is expressed
as square meters.
• Area can also be expressed as cubic centimeters.
• What is the area of a rectangle that has an a
length of 6 cm and a width of 16 cm?
• 16 cm
• 1 6 cm
• 11111cmam

11
Volume
• Volume is the amount of space occupied by an
object. The derived SI unit for volume is cubic
meters. The cubic meter is rather large, so a
more common unit of cubic centimeters is more
commonly used.
• Non-SI units are also used to measure volume such
as the milliliter (mL) and the liter (L), which
is 1000 cm3. There are 1000 mL in 1 L.
• Beakers, flasks, and graduated cylinders are
often used to determine the volume of liquids.

12
density
• Density is the ratio of mass to volume, or mass
divided by volume. It can be written
• densitymass/volume or Dm/V
• Density is a characteristic physical property
of a substance that does not depend on the size
of the sample. As the mass of an object
increases, its volume increases.
• Question Are raisins, more or less dense than
soda water? Lets see!

13
Name Volume (cm3) Mass (kg)
Michael 120384 85
John 77509 59
Colleen 35000 56
Fabrizio 135456 80
Abella 47824 62
Aaron 174096 101
Felicita 95700 63
Travis 89775 102
Franklin 97559 70
Steven 90580 70
Kayla 90180 65
Nicholas 89280 66
Brianna 100200 70
14
Name Volume X Mass Y
Oscar 109620 cm3 74kg 0.000235
Crystal 69,900 cm3 51kg 0.0002857
Ron 172,900 cm3 79kg 0.000222
Brian 170280 cm3 74kg 0.0002
Chevon 126412 cm3 65kg 0.000211
Amber 94350 cm3 0.0002
Maria 56160cm3 49kg 0.0002
Danielle 115520 cm3
Robert 131760cm3 60kg 0.00021
Emmanuel 129960 cm3 62kg 0.000192
Brittany 95456 cm3 55kg 0.00027
Alyssa 110160 cm3 0.00027
Jaclynne 65490 cm3 50kg 0.0003
Jake 142740 cm3 67kg 0.0003