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7/30/2019 1.1 1.2 Introduction
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Chapter 1: Introduction to
Physics
1.1 Understanding Physics
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1.1 Understanding Physics
1. Like all sciences, physics is based on experimental
observationsand quantitative measurements.
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1.1 Understanding Physics
2. Historically, until nineteenth century,
physics was called natural philosophy.
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1.1 Understanding Physics
3. Physics is a branch of science concerningstudy of natural phenomena, that is, properties
of matter and energy.
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1.1 Understanding Physics
4. Some examples of natural phenomena
are
(a) sunrise and sunset,
(b) lightning and thunder,
(c) rainbow and blue sky,
(d) earthquake and tsunami.
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Field of study in Physics
1 In general, physics is concerned with the
study of energy and the properties and
structure ofmatter.
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Field of study in Physics
2 The fields of study in physics can be
divided into classicalphysics and modern
physics.
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Field of study in Physics
3 Classical physics deals with questions regarding
motionand energy. It includes five important areas:
mechanics (forces and motion), heat, sound, electricityand magnetism, and light.
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Field of study in Physics
4 Modern physics concentrates on scientificbeliefs about thebasic structure of the material
world. Its major fields include atomic, molecularand electron physics, nuclear physics, particlephysics, relativity, origin of the universe, andastrophysics.
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Chapter 1
1.1.2 Understanding Base Quantitiesand rived Quantities
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Base Quantities
1. Physical quantities are quantities that
can be measured.
i i
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Base Quantities
2. A physical quantity can be represented by a symbol of
the quantity, a numerical value for the magnitude of the
quantity and the unitof measurement of the quantity.
Length, l= 1.67 m
l- symbol 1.67is the value m - unit
Q i i
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Base Quantities
3. Base quantitiesare physical quantities
that cannot be defined in terms of otherquantities.
Base quantity :
Length
Derived quantity :
Area = length x length
B Q i i
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Base Quantities
4. Table 1.1 shows five base quantities and
their respective SI units.
B Q i i
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Base Quantities
Base quantities SI base units
Name Symbol Name Symbol
Length l Metre m
Mass m Kilogram Kg
Time t Second s
Electric
current
I Ampere A
Temperature T Kelvin K
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Derived Quantities 1 Derived quantitiesare physical quantities derived
from base quantities by multiplication or division or both.
The unit for a derived quantity is known as aderived unit.
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Derived Quantities
2 Table 1.2 shows some examples of derived quantities
and their corresponding derived units. Several derived
units are complex. Special names are substituted for these
units. For example, the unit for the derived quantity, force,
is the newton (N).
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Derived Quantities
takenTime
ntDisplaceme
takenTimevelocityinChange
s
ms-1
volume
Masskg
m3
Derived quantities Derived units
Area = Length x breadth [Area] = m x m = m2
Velocity = [Velocity] =
= ms1
Acceleration=
Density = [Density] = = kgm3
m
s
[Acceleration] =
= ms2
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Scientific Notation 1 Scientists have developed a shorter method of
expressing very large or very small numbers. This method
is called scientific notationor standard form.
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Scientific Notation 2 Scientific notationis based on powers of the
base number 10. The scientific notation in
standard form is written as:
A x 10n
where
(a) 1 A < 10 and A can be an integer or decimal number. (b) n is a positive integer for a number greater than one or
a negative integer for a number less than one.
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Prefixes 1. Prefixes are used to simplify the
description of physical quantities that are
eithervery big orvery small.
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Prefixes
2. It is not easy to figure out a distance of
100 000 mm. Neither it is easy to imagine
the size of an atom which has a radius of
0.0000005 m.
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Prefixes
3. Table 1.3 lists some commonly used SI prefixes.
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Prefixes
Prefix Symbols Power/factor Value
Giga- G 109 1 000 000 000
Mega- M 106 1 000 000
Kilo- k 103 1 000
Deci- d 10-1 0.1
Centi- c 10-2 0.01
Milli- m 10-3 0.001
Micro- 10-6 0.000 001
Nano- n 10-9 0.000 000 001