Physics Notes PCS System
CHP # 1 PHYSICAL QUANTITIES AND MEASUREMENT
Q.1 What is physics? Describe its main branches.
Ans. Physics
The branch of science which deals with the study of properties of matter,
energy and their mutual relationship is called physics.
Main branches of physics are;
(1) Mechanics
The branch of physics that deals with the study of motion of material
objects under the action of forces.
(2) Heat and Thermodynamics
The branch of physics which deals with the transformation of heat energy
into other forms of energy.
(3) Optics
The branch of physics which deals with the nature of light, its propagation,
reflection, refraction, dispersion and the wave properties of light.
(4) Electricity and magnetism
It deals with the study of static as well as moving charges and the
phenomena that occurs due to the effects of charges.
(5) Atomic physics
The branch of physics which deals with the structure and properties of
individual atoms.
Q.2 What is physical quantity? Describe its types.
Ans. Physical quantity
A quantity which can be easily observed and measured is called physical
quantity. For example
Distance, mass, time, Area, Volume, etc.
There are two types of physical quantities;
(1) Base physical quantities
Those physical quantities which are the simplest standards selected by
the scientists for other quantities are called base or standard physical
quantities. For examples
Length, mass, time, electric current, temperature, etc.
(2) Derived physical quantities
Those physical quantities which are obtained by multiplying or dividing the
base physical quantities are called derived physical quantities.
For examples
Force, Area, Volume, speed, acceleration etc.
, Physics Notes PCS System
Q.3 What is international system of units?
Ans. The set of units used for the physical quantities are called system of units.
The system of units in which the unit of length, mass and time is meter,
kilogram and second respectively is called system international (SI).
It is based on seven basic units from which all other units are derived.
Q.4 What are prefixes? Explain
Ans. Prefixes
In scientific calculation some time we have to deal with quantities that are
either very large or small compared with the base units, in such cases we
use higher or smaller units of the standard unit. These smaller or higher
units are in power of 10 which are called prefixes. For examples
The distance between two cities is taken in kilometer rather than in meter.
The thickness of a wire is taken in millimeter rather than in meter.
Table of prefixes
Sub Multiples prefix symbol Multiples prefix symbol
-1 1
10 deci d 10 deca da
10-2 centi c 102 hecto h
-3 3
10 milli m 10 kilo K
10-6 micro µ 106 mega M
-9 9
10 nano n 10 giga G
-12 12
10 pico p 10 tera T
10-15 femto f 1015 peta P
-18 18
10 atto a 10 exa E
Q.5 State and explain what is scientific notation?
Ans. Scientific Notation
Every small or large number “N” can be expressed in terms of number “M”
multiplied by the negative or positive power of 10 as follow:
N = M 10n
Where n = 0, 1 , 2 , 3 , 4 ,…………
It must be noted that the first digit of “M” from left to the right is non zero
digit.
In a given number N, move the decimal point and place it after the first
non zero digit.
If the decimal point is moved towards left from its given initial position,
then the power of 10 will be positive.
Similarly if the decimal point is moved towards right from its given initial
position, then the power of 10 will be negative. For examples
The mass of moon is 70000000000000000000000Kg.
In scientific Notation
= 7 1022Kg.
CHP # 1 PHYSICAL QUANTITIES AND MEASUREMENT
Q.1 What is physics? Describe its main branches.
Ans. Physics
The branch of science which deals with the study of properties of matter,
energy and their mutual relationship is called physics.
Main branches of physics are;
(1) Mechanics
The branch of physics that deals with the study of motion of material
objects under the action of forces.
(2) Heat and Thermodynamics
The branch of physics which deals with the transformation of heat energy
into other forms of energy.
(3) Optics
The branch of physics which deals with the nature of light, its propagation,
reflection, refraction, dispersion and the wave properties of light.
(4) Electricity and magnetism
It deals with the study of static as well as moving charges and the
phenomena that occurs due to the effects of charges.
(5) Atomic physics
The branch of physics which deals with the structure and properties of
individual atoms.
Q.2 What is physical quantity? Describe its types.
Ans. Physical quantity
A quantity which can be easily observed and measured is called physical
quantity. For example
Distance, mass, time, Area, Volume, etc.
There are two types of physical quantities;
(1) Base physical quantities
Those physical quantities which are the simplest standards selected by
the scientists for other quantities are called base or standard physical
quantities. For examples
Length, mass, time, electric current, temperature, etc.
(2) Derived physical quantities
Those physical quantities which are obtained by multiplying or dividing the
base physical quantities are called derived physical quantities.
For examples
Force, Area, Volume, speed, acceleration etc.
, Physics Notes PCS System
Q.3 What is international system of units?
Ans. The set of units used for the physical quantities are called system of units.
The system of units in which the unit of length, mass and time is meter,
kilogram and second respectively is called system international (SI).
It is based on seven basic units from which all other units are derived.
Q.4 What are prefixes? Explain
Ans. Prefixes
In scientific calculation some time we have to deal with quantities that are
either very large or small compared with the base units, in such cases we
use higher or smaller units of the standard unit. These smaller or higher
units are in power of 10 which are called prefixes. For examples
The distance between two cities is taken in kilometer rather than in meter.
The thickness of a wire is taken in millimeter rather than in meter.
Table of prefixes
Sub Multiples prefix symbol Multiples prefix symbol
-1 1
10 deci d 10 deca da
10-2 centi c 102 hecto h
-3 3
10 milli m 10 kilo K
10-6 micro µ 106 mega M
-9 9
10 nano n 10 giga G
-12 12
10 pico p 10 tera T
10-15 femto f 1015 peta P
-18 18
10 atto a 10 exa E
Q.5 State and explain what is scientific notation?
Ans. Scientific Notation
Every small or large number “N” can be expressed in terms of number “M”
multiplied by the negative or positive power of 10 as follow:
N = M 10n
Where n = 0, 1 , 2 , 3 , 4 ,…………
It must be noted that the first digit of “M” from left to the right is non zero
digit.
In a given number N, move the decimal point and place it after the first
non zero digit.
If the decimal point is moved towards left from its given initial position,
then the power of 10 will be positive.
Similarly if the decimal point is moved towards right from its given initial
position, then the power of 10 will be negative. For examples
The mass of moon is 70000000000000000000000Kg.
In scientific Notation
= 7 1022Kg.
