This document provides an overview of physical quantities and the International System of Units (SI) for measuring them. It defines physical quantities as things that can be measured with a magnitude and unit. The SI is standardized by the General Conference on Weights and Measures and uses seven base units: meter, kilogram, second, ampere, kelvin, candela, and mole. Derived quantities are defined in terms of base units, like speed being meters/second. Prefixes are used to modify units for very small or large numbers. The document gives examples of derived quantities and their units, like area being square meters.

1. Unit 1
Physics IAL
Physical Quantities

2. Outcomes
• Physical Quantities
• International System of Units (SI)
• Basic and Derived Quantities
• Standards in SI
• Instruments for Measurement.
• Representation of Measurements.
• Prefixes and their uses
Students will be able to understand:
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3. Physical Quantities
A physical quantity is one that can be measured/observed
and consists of a magnitude and unit.
70
km/h

4.5 m

Quantity : Height(Length)
Magnitude : 4.5
Unit : meter (m)
Quantity : Speed
Magnitude : 70
Unit : kilometer per hour
Quantity : Temperature
Magnitude : 33
Unit : celcius
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4. More Examples of Physical Quantities
Time
Weight
Energy
Volume
Area
Pressure
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5. Measurement of Physical Quantities
Physics is all about the observation and
measurement of nature / physical quantities.
Types of Observations: Qualitative and Quantitative
Example: The new iPhone 5s is expensive. Its price
is R.O. 270
Example: Ali is a tall boy. His height is 6 feet.
Example: The land area of Monaco is small and it is
densely populated. It has an area of 1.98 km2 with a
population of 35,986
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6. Standard for Measurements
Every measurement must have a standard !!!
Every Standard must have the following properties
Invariable
+
Accessible
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7. The General Conference on Weights and Measures
(CGMP) is responsible for the definition of the SI units.
First Meeting : 1883
23rd Meeting : 2010
Next Expected: 2015
International System of Units (SI)
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8. Types of SI Units
Basic Quantities are the building blocks but the
Derived Quantities are made from the Basic.
Supplementary Quantities are not still decided-
whether in Basic or Derived
Basic Derived Supplementary
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9. Basic SI Quantities and Units
Quantity SI Unit Symbol of Unit
Length meter m
Mass kilogram kg
Time second s
Electric Current ampere A
Thermodynamic Temperature kelvin K
Luminous Intensity candela cd
Amount of Substance mole mol
Similar table : Table 1-15, P-10 (Giancoli)
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10. Some Derived SI Quantities and Units
Quantity SI Unit Symbol of Unit
Speed meter per second m s-1
Force newton N
Acceleration meter per sec per sec m s-2
Area square meter m2
Pressure pascal Pa
Volume cubic meter m3
Many More . . .
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11. Examples of Derived SI Quantities and Units
11
Defining equation: area = length × width
In terms of units: Units of area = m × m = m2
Defining equation: volume = length × width ×height
In terms of units: Units of volume = m×m×m = m3
Defining equation: density = mass ÷ volume
In terms of units: Units of density = kg/m3=kg m−3

12. 12
Work out the derived quantities for:
Defining equation: speed = distance / time
In terms of units: Units of speed =
Defining equation: pressure = force / area
In terms of units: Units of pressure =
Defining equation: force = mass × acceleration
In terms of units: Units of force =
Practice: Derived SI Quantities

13. Supplementary SI Quantities and Units
Quantity SI Unit Symbol of Unit
Plane Angle radian rad
Spherical Angle steradian str
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14. Prefixes
To represent very small or very large numbers the prefixes
can be used.
Name Symbol Number Powers of 10
tera T 1 000 000 000 000 1012
giga G 1 000 000 000 109
mega M 1 000 000 106
kilo k 1 000 103
hecto h 1 00 102
micro µ 0.000 001 10-6
nano n 0.000 000 001 10-9
pico p 0.000 000 000 001 10-12
deca da 1 0 101
1 10 0
deci d 0.1 10-1
centi c 0.01 10-2
milli m 0.001 10-3
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15. Practice Questions
1. Find at least 5 derived quantities and write the SI
units
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2. Write the following quantities using suitable prefixes.
a. 5 000000 J b. 5000 g c. 0.009 s
3. How many meters in a kilometer?
4. How many second in a microsecond?