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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