# Chapter 1_ Introduction to Physics_1_

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```					Chapter 1: Introduction to
Physics

1.1 Understanding Physics
1.1 Understanding Physics

   1. Like all sciences, physics is based on experimental
observations and quantitative measurements.
1.1 Understanding Physics

   2. Historically, until nineteenth century,
physics was called natural philosophy.

1.1 Understanding Physics

   3. Physics is a branch of science concerning
study of natural phenomena, that is, properties
of matter and energy.

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.
Field of study in Physics

   1 In general, physics is concerned with the
study of energy and the properties and
structure of matter.

Field of study in Physics

   2 The fields of study in physics can be
divided into classical physics and modern
physics.
Field of study in Physics

   3 Classical physics deals with questions regarding
motion and energy. It includes five important areas:
mechanics (forces and motion), heat, sound, electricity
and magnetism, and light.

Field of study in Physics

   4 Modern physics concentrates on scientific
beliefs about the basic structure of the material
world. Its major fields include atomic, molecular
and electron physics, nuclear physics, particle
physics, relativity, origin of the universe, and
astrophysics.
Chapter 1

1.1.2 Understanding Base Quantities
and rived Quantities
Base Quantities

   1. Physical quantities are quantities that
can be measured.
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 unit of measurement of the quantity.


Length, l = 1.67 m

l - symbol    1.67is the value    m - unit
Base Quantities
   3. Base quantities are physical quantities
that cannot be defined in terms of other
quantities.

Base quantity :   Derived quantity :
Length            Area = length x length
Base Quantities
   4. Table 1.1 shows five base quantities and
their respective SI units.
Base Quantities
Base quantities            SI base units

Name           Symbol      Name           Symbol

Length                l    Metre               m

Mass             m       Kilogram             Kg

Time                 t   Second               s

Electric              I   Ampere               A
current
Temperature         T        Kelvin              K
Derived Quantities
   1 Derived quantities are physical quantities derived
from base quantities by multiplication or division or both.
The unit for a derived quantity is known as a derived unit.
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).
Derived Quantities
Derived quantities                       Derived units

Area = Length x breadth            [Area] = m x m = m2

m
Velocity = Displacement            [Velocity] =
Time taken          = ms–1         s
-1
Acceleration=                       [Acceleration] = ms
Change in velocity
Time taken         = ms–2            s

Density = Mass                     [Density] = kg = kgm–3
3
m
volume
Scientific Notation
   1 Scientists have developed a shorter method of
expressing very large or very small numbers. This method
is called scientific notation or standard form.

Distance from house to school : 5 000 m
Scientific Notation
   2 Scientific notation is 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.
Prefixes
   1. Prefixes are used to simplify the
description of physical quantities that are
either very big or very small.
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.
Prefixes

   3. Table 1.3 lists some commonly used SI prefixes.

Ram : 512 Mb                     HD : 80 Gb
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-      μ           10-6       0.000 001

Nano-        n          10-9       0.000 000 001

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