CHAPTER-1
MEASUREMENTS AND EXPERIMENTATION
Topic-1 International System of Units
Revision Notes
➢➢ SI Units: Internationally accepted system of physical units based on the
metre, kilogram, second, ampere, candela, kelvin and mole.
➢➢ Measurement is the process of comparison of the given physical quantity with the known standard quantity of the
same nature.
Unit is the quantity of a constant magnitude which is used to measure the magnitudes of other quantities of the
same nature.
Physical quantity = ( numerical value) × (unit)
Fundamental or basic units : A fundamental (or basic) unit is that which is independent of any other unit or
which can neither be changed nor can be related to any other fundamental unit.
Derived units : These are those units which depend on the fundamental units or which can be expressed in
terms of the fundamental units.
System of units :
(i) CGS system (or French system)
(ii) FPS system (or British system)
(iii) MKS system (or Metric system)
(iv) S.I. (or International system)
Fundamental quantities, units and symbols in SI system
➢➢ Fundamental Units
Quantity Unit Symbol
Length metre m
Mass kilogram kg
Time second s
Temperature kelvin K
Luminous Intensity candela cd
Electric Current ampere A
Amount of substance mole mol
Angle radian rd
Solid angle steradian st-rd
Prefix used for big measurements
Prefix Symbol Meaning
deca Da 101
hecto h 102
,2 Oswaal ICSE Revision Notes Chapterwise & Topicwise, PHYSICS, Class-IX
kilo k 103
mega M 106
giga G 109
tera T 1012
peta P 1015
exa E 1018
zetta Z 1021
yotta Y 1024
Prefixes used for small measurements
Prefix Symbol Meaning
deci d 10–1
centi c 10–2
milli m 10–3
micro µ 10–6
nano n 10–9
pico p 10–12
femto f 10–15
atto a 10–18
zepto z 10–21
yotto y 10–24
➢➢ Non metric unit of length
Astronomical unit (AU): One astronomical unit is equal to the mean distance between the earth and sun i.e.,
1 AU = 1.496 × 1011 metre
Light year : A light year is the distance travelled by light in vacuum in one year i.e.,
1 light year = speed of light × time (1 year)
1 ly = 9.46 × 1012 km
Parsec : One parsec is the distance from where the semi major axis of orbit or earth subtends an angle of one
second. 1 parsec= 3.26 ly
➢➢ Non metric unit of mass
The mass of atomic particles such as proton, neutron and electron is expressed is a unit called the atomic mass
unit or the unified atomic mass unit.
1
It is defined as 1 amu (or u) is th the mass of one Carbon-12 atom.
12
The mass of large heavenly bodies is measured in terms of solar mass where 1 solar mass is the mass of the sun
i.e., 1 solar mass = 2 × 1030 kg
➢➢ Units of Time
SI unit of time is second (s)
smaller units of time
1 ms = 10–3s; 1 µs = 10–6s
1 shake = 10–8s ; 1 ns = 10–9s
bigger units of time
� minute: one minute is the duration of 60 seconds.
� hour: one hour in the duration of 60 minutes.
� day: the time taken by the earth to rotate once on its own axis is called a day.
� lunar month: the time of one lunar cycle is 29.5 days.
� month: a month considered to be of 30 days.
, Oswaal ICSE Revision Notes Chapterwise & Topicwise, PHYSICS, Class-IX 3
� year: one year is defined as the time in which the earth completes one revolution around the sun.
� leap year: a leap year is the year in which the month of February is of 29 days.
� decade: a decade is of 10 years.
� century: a century is of 100 years.
� millennium: a millennium is of 1000 years.
Derived Units of physical quantities
Quantity Derived unit Symbol
Volume metre × metre × metre m3
Force mass × acceleration kgms–2 or N
Energy
(metre)2 kgm2s–2 or J
kilogram ×
sec ond2
1
Frequency or second–1 s–1 or Hz
sec ond
Mnemonics
Concept Name: S.I. units
Mnemonics: Keka, Calls Mimo
Interpretations: Kilogram, Kelvin, Ampere, Candela, Second, Meter, Mol
Topic-2 Simple Pendulum
Revision Notes
➢➢ A simple pendulum is a heavy point mass (known as bob) suspended from a rigid support by a massless and
inextensible string.
➢➢ Relationship between time period and frequency
1 1
f= Or T =
T f
➢➢ The time taken for one oscillation is known as the Time period (T)
l
T = 2π
g
➢➢ Here l is the effective length and g is the acceleration due to gravity at that place where time period is defined.
➢➢ Factors affecting the time period of a simple pendulum:
– The time period of oscillation is directly proportional to the square root of its effective length.
– The time period of oscillation inversely proportional to the square root of acceleration due to gravity.
– The time period of oscillation does not depend on the mass or material or the body suspended.
– The time period of oscillation does not depend on the extent of swing or either side side (i.e., amplitude)
➢➢ Second’s pendulum
A pendulum with a time period of oscillation equal to two seconds is known as a second’s pendulum.
Key Words
➢➢ The time period of oscillation does not depend on the mass or material of the body suspended (i.e., bob)
➢➢ The time period of oscillation does not depend on the extent of swing on either side (i.e., amplitude)
MEASUREMENTS AND EXPERIMENTATION
Topic-1 International System of Units
Revision Notes
➢➢ SI Units: Internationally accepted system of physical units based on the
metre, kilogram, second, ampere, candela, kelvin and mole.
➢➢ Measurement is the process of comparison of the given physical quantity with the known standard quantity of the
same nature.
Unit is the quantity of a constant magnitude which is used to measure the magnitudes of other quantities of the
same nature.
Physical quantity = ( numerical value) × (unit)
Fundamental or basic units : A fundamental (or basic) unit is that which is independent of any other unit or
which can neither be changed nor can be related to any other fundamental unit.
Derived units : These are those units which depend on the fundamental units or which can be expressed in
terms of the fundamental units.
System of units :
(i) CGS system (or French system)
(ii) FPS system (or British system)
(iii) MKS system (or Metric system)
(iv) S.I. (or International system)
Fundamental quantities, units and symbols in SI system
➢➢ Fundamental Units
Quantity Unit Symbol
Length metre m
Mass kilogram kg
Time second s
Temperature kelvin K
Luminous Intensity candela cd
Electric Current ampere A
Amount of substance mole mol
Angle radian rd
Solid angle steradian st-rd
Prefix used for big measurements
Prefix Symbol Meaning
deca Da 101
hecto h 102
,2 Oswaal ICSE Revision Notes Chapterwise & Topicwise, PHYSICS, Class-IX
kilo k 103
mega M 106
giga G 109
tera T 1012
peta P 1015
exa E 1018
zetta Z 1021
yotta Y 1024
Prefixes used for small measurements
Prefix Symbol Meaning
deci d 10–1
centi c 10–2
milli m 10–3
micro µ 10–6
nano n 10–9
pico p 10–12
femto f 10–15
atto a 10–18
zepto z 10–21
yotto y 10–24
➢➢ Non metric unit of length
Astronomical unit (AU): One astronomical unit is equal to the mean distance between the earth and sun i.e.,
1 AU = 1.496 × 1011 metre
Light year : A light year is the distance travelled by light in vacuum in one year i.e.,
1 light year = speed of light × time (1 year)
1 ly = 9.46 × 1012 km
Parsec : One parsec is the distance from where the semi major axis of orbit or earth subtends an angle of one
second. 1 parsec= 3.26 ly
➢➢ Non metric unit of mass
The mass of atomic particles such as proton, neutron and electron is expressed is a unit called the atomic mass
unit or the unified atomic mass unit.
1
It is defined as 1 amu (or u) is th the mass of one Carbon-12 atom.
12
The mass of large heavenly bodies is measured in terms of solar mass where 1 solar mass is the mass of the sun
i.e., 1 solar mass = 2 × 1030 kg
➢➢ Units of Time
SI unit of time is second (s)
smaller units of time
1 ms = 10–3s; 1 µs = 10–6s
1 shake = 10–8s ; 1 ns = 10–9s
bigger units of time
� minute: one minute is the duration of 60 seconds.
� hour: one hour in the duration of 60 minutes.
� day: the time taken by the earth to rotate once on its own axis is called a day.
� lunar month: the time of one lunar cycle is 29.5 days.
� month: a month considered to be of 30 days.
, Oswaal ICSE Revision Notes Chapterwise & Topicwise, PHYSICS, Class-IX 3
� year: one year is defined as the time in which the earth completes one revolution around the sun.
� leap year: a leap year is the year in which the month of February is of 29 days.
� decade: a decade is of 10 years.
� century: a century is of 100 years.
� millennium: a millennium is of 1000 years.
Derived Units of physical quantities
Quantity Derived unit Symbol
Volume metre × metre × metre m3
Force mass × acceleration kgms–2 or N
Energy
(metre)2 kgm2s–2 or J
kilogram ×
sec ond2
1
Frequency or second–1 s–1 or Hz
sec ond
Mnemonics
Concept Name: S.I. units
Mnemonics: Keka, Calls Mimo
Interpretations: Kilogram, Kelvin, Ampere, Candela, Second, Meter, Mol
Topic-2 Simple Pendulum
Revision Notes
➢➢ A simple pendulum is a heavy point mass (known as bob) suspended from a rigid support by a massless and
inextensible string.
➢➢ Relationship between time period and frequency
1 1
f= Or T =
T f
➢➢ The time taken for one oscillation is known as the Time period (T)
l
T = 2π
g
➢➢ Here l is the effective length and g is the acceleration due to gravity at that place where time period is defined.
➢➢ Factors affecting the time period of a simple pendulum:
– The time period of oscillation is directly proportional to the square root of its effective length.
– The time period of oscillation inversely proportional to the square root of acceleration due to gravity.
– The time period of oscillation does not depend on the mass or material or the body suspended.
– The time period of oscillation does not depend on the extent of swing or either side side (i.e., amplitude)
➢➢ Second’s pendulum
A pendulum with a time period of oscillation equal to two seconds is known as a second’s pendulum.
Key Words
➢➢ The time period of oscillation does not depend on the mass or material of the body suspended (i.e., bob)
➢➢ The time period of oscillation does not depend on the extent of swing on either side (i.e., amplitude)
