HC Verma Summary: Introduction to Physics | Physics Class 11 - NEET PDF Download

 Page 1


1 What is Ph ysics?
Ph ysics is the study of how the world around us works. Nature is full of fasci-
nating things lik e the wind blowing, the sun shining, the planets moving, and
even how our bodies function. These are all called phenomena . Ph ysics helps
us understand these phenomena b y finding the basic rules, or laws , that govern
them.
F o r example, wh y does an apple fall from a tree? Wh y does the moon orbit the
Earth? These events follow rules lik e Newton’ s laws of motion and gr avitation.
B y discovering these rules, ph ysicists explain wh y things happen the wa y they
do. Ph ysics applies to everything, from tin y atoms to huge galaxies, and even
helps in fields lik e biology and medicine.
Think of ph ysics as a game where nature is the pla yer , and we are observers
trying to figure out the rules b y watching what happens. Sometimes, we guess a
rule, but new observations might show it’ s wrong, so we update it. Great scien-
tists lik e Newton and Einstein became famous b y guessing rules that explained
what t hey saw .
K ey Idea : Ph ysics is real because it studies nature directly . No one mak es up the
rules; we discover them through observation and experiments.
1.1 Solved Example: Understanding Phenomena
Question : A ball is thrown upward and comes back down. Which ph ysics law
explains this motion?
Solution : The ball’ s motion is explained b y Newton’ s law of gr avitation , which
sa ys that objects are pulled toward the Earth b y gr avity . When you throw the
ball up, gr avity pulls it back down, following a predictable path. This is a basic
rule of ph ysics that governs falling objects.
1
Page 2


1 What is Ph ysics?
Ph ysics is the study of how the world around us works. Nature is full of fasci-
nating things lik e the wind blowing, the sun shining, the planets moving, and
even how our bodies function. These are all called phenomena . Ph ysics helps
us understand these phenomena b y finding the basic rules, or laws , that govern
them.
F o r example, wh y does an apple fall from a tree? Wh y does the moon orbit the
Earth? These events follow rules lik e Newton’ s laws of motion and gr avitation.
B y discovering these rules, ph ysicists explain wh y things happen the wa y they
do. Ph ysics applies to everything, from tin y atoms to huge galaxies, and even
helps in fields lik e biology and medicine.
Think of ph ysics as a game where nature is the pla yer , and we are observers
trying to figure out the rules b y watching what happens. Sometimes, we guess a
rule, but new observations might show it’ s wrong, so we update it. Great scien-
tists lik e Newton and Einstein became famous b y guessing rules that explained
what t hey saw .
K ey Idea : Ph ysics is real because it studies nature directly . No one mak es up the
rules; we discover them through observation and experiments.
1.1 Solved Example: Understanding Phenomena
Question : A ball is thrown upward and comes back down. Which ph ysics law
explains this motion?
Solution : The ball’ s motion is explained b y Newton’ s law of gr avitation , which
sa ys that objects are pulled toward the Earth b y gr avity . When you throw the
ball up, gr avity pulls it back down, following a predictable path. This is a basic
rule of ph ysics that governs falling objects.
1
2 Ph ysics and Mathematics
Ph ysics and mathematics go hand in hand. Mathematics is lik e a language that
mak es it easier to describe the rules of nature. F or example, instead of sa ying,
”The force between two objects depends on their masses and the distance be-
tween them,” we can write a simple equation:
F ?
m
1
m
2
r
2
This equation sa ys the force (F ) is proportional t o the product of the masses
(m
1
m
2
) and inversely proportional to the square of the distance (r
2
). U sing math,
we can mak e predictions. F or instance, we can calculate the force between two
objects or how an object moves.
Mathematics is a tool, lik e a comfortable bus that helps us tr avel to our destination—
understanding nature. Without math, explaining ph ysics would be much harder ,
but the main goal is alwa ys to understand the natur al world, not just to do math.
K ey Idea : Mathematics is the language of ph ysics, making it easier to describe
and p redict natur al phenomena.
2.1 Solved Example: Using Mathematics in Ph ysics
Question : The force between t wo masses of 5 kg and 10 kg, separ ated b y 2 m, is
given b yF =
Gm
1
m
2
r
2
, whereG = 6.67×10
-11
N· m
2
/ kg
2
. Calculate the force.
Solution :
F =
(6.67×10
-11
)×5×10
2
2
=
6.67×10
-11
×50
4
=
3.335×10
-9
4
= 8.34×10
-10
N
The force is 8.34×10
-10
N.
3 Units
Ph ysics involves measuring things lik e length, mass, or time. T o measure an y-
thing, we need a standard unit. F or example, to know how much heavier an
elephant is compared to a goat, we choose a unit of mass (lik e a kilogr am). If
an elephant is 2000 k g and a goat is 50 k g, the elephant is 2000÷ 50 = 40 times
heavier .
A measurement has two parts: a number (how man y times the unit) and the unit
itself. F or example, ”3 meters” means 3 times the unit of length called a meter .
2
Page 3


1 What is Ph ysics?
Ph ysics is the study of how the world around us works. Nature is full of fasci-
nating things lik e the wind blowing, the sun shining, the planets moving, and
even how our bodies function. These are all called phenomena . Ph ysics helps
us understand these phenomena b y finding the basic rules, or laws , that govern
them.
F o r example, wh y does an apple fall from a tree? Wh y does the moon orbit the
Earth? These events follow rules lik e Newton’ s laws of motion and gr avitation.
B y discovering these rules, ph ysicists explain wh y things happen the wa y they
do. Ph ysics applies to everything, from tin y atoms to huge galaxies, and even
helps in fields lik e biology and medicine.
Think of ph ysics as a game where nature is the pla yer , and we are observers
trying to figure out the rules b y watching what happens. Sometimes, we guess a
rule, but new observations might show it’ s wrong, so we update it. Great scien-
tists lik e Newton and Einstein became famous b y guessing rules that explained
what t hey saw .
K ey Idea : Ph ysics is real because it studies nature directly . No one mak es up the
rules; we discover them through observation and experiments.
1.1 Solved Example: Understanding Phenomena
Question : A ball is thrown upward and comes back down. Which ph ysics law
explains this motion?
Solution : The ball’ s motion is explained b y Newton’ s law of gr avitation , which
sa ys that objects are pulled toward the Earth b y gr avity . When you throw the
ball up, gr avity pulls it back down, following a predictable path. This is a basic
rule of ph ysics that governs falling objects.
1
2 Ph ysics and Mathematics
Ph ysics and mathematics go hand in hand. Mathematics is lik e a language that
mak es it easier to describe the rules of nature. F or example, instead of sa ying,
”The force between two objects depends on their masses and the distance be-
tween them,” we can write a simple equation:
F ?
m
1
m
2
r
2
This equation sa ys the force (F ) is proportional t o the product of the masses
(m
1
m
2
) and inversely proportional to the square of the distance (r
2
). U sing math,
we can mak e predictions. F or instance, we can calculate the force between two
objects or how an object moves.
Mathematics is a tool, lik e a comfortable bus that helps us tr avel to our destination—
understanding nature. Without math, explaining ph ysics would be much harder ,
but the main goal is alwa ys to understand the natur al world, not just to do math.
K ey Idea : Mathematics is the language of ph ysics, making it easier to describe
and p redict natur al phenomena.
2.1 Solved Example: Using Mathematics in Ph ysics
Question : The force between t wo masses of 5 kg and 10 kg, separ ated b y 2 m, is
given b yF =
Gm
1
m
2
r
2
, whereG = 6.67×10
-11
N· m
2
/ kg
2
. Calculate the force.
Solution :
F =
(6.67×10
-11
)×5×10
2
2
=
6.67×10
-11
×50
4
=
3.335×10
-9
4
= 8.34×10
-10
N
The force is 8.34×10
-10
N.
3 Units
Ph ysics involves measuring things lik e length, mass, or time. T o measure an y-
thing, we need a standard unit. F or example, to know how much heavier an
elephant is compared to a goat, we choose a unit of mass (lik e a kilogr am). If
an elephant is 2000 k g and a goat is 50 k g, the elephant is 2000÷ 50 = 40 times
heavier .
A measurement has two parts: a number (how man y times the unit) and the unit
itself. F or example, ”3 meters” means 3 times the unit of length called a meter .
2
3.1 Who Decides Units?
Units need to be the same worldwide so everyone can understand measure-
ments. An international group called the Gener al Confer ence on W eights and
Measur es (CGPM) decides the standard units. These are published and used glob-
ally .
3.2 Fundamental and Derived Units
Not all quantities need their own unit. W e choose a few fundamental quantities
(lik e length, mass, and time) that are independent. Other quantities, lik e area
or speed, are derived from these. F or example: - Area : If the unit of length is a
meter , the unit of area is a square meter (m
2
). - Speed : If length is in meters and
time is in seconds, speed is in meters per second (m/ s).
There are seven fundamental quantities in the SI system (International S ystem
of Units), widely used around the world. They are listed below:
T able 1: Fundamental Quantities and SI Units
Quantity Unit Name S ymbol
Length metre m
Mass kilogr am k g
Time second s
Electric Current ampere A
Thermodynamic T emper ature k elvin K
Amount of Substance mole mol
Luminous Intensity candela c d
Two additional units are: - Plane angle : r adian (r ad) - Solid angle : ster adian
(sr)
3.3 SI Prefixes
Ph ysical quantities can be very large or very small. F or example, the distance
between stars is huge, while the size of an atom is tin y . T o handle this, we use
prefixes with SI units, lik e kilo (k) for 1000 or milli (m) for 1/1000. Here are some
common prefixes:
3.4 Solved Example: Using Units
Question : A car tr avels 150 km in 2 h. Calculate its speed in m/ s.
Solution :
Speed =
Distance
Time
3
Page 4


1 What is Ph ysics?
Ph ysics is the study of how the world around us works. Nature is full of fasci-
nating things lik e the wind blowing, the sun shining, the planets moving, and
even how our bodies function. These are all called phenomena . Ph ysics helps
us understand these phenomena b y finding the basic rules, or laws , that govern
them.
F o r example, wh y does an apple fall from a tree? Wh y does the moon orbit the
Earth? These events follow rules lik e Newton’ s laws of motion and gr avitation.
B y discovering these rules, ph ysicists explain wh y things happen the wa y they
do. Ph ysics applies to everything, from tin y atoms to huge galaxies, and even
helps in fields lik e biology and medicine.
Think of ph ysics as a game where nature is the pla yer , and we are observers
trying to figure out the rules b y watching what happens. Sometimes, we guess a
rule, but new observations might show it’ s wrong, so we update it. Great scien-
tists lik e Newton and Einstein became famous b y guessing rules that explained
what t hey saw .
K ey Idea : Ph ysics is real because it studies nature directly . No one mak es up the
rules; we discover them through observation and experiments.
1.1 Solved Example: Understanding Phenomena
Question : A ball is thrown upward and comes back down. Which ph ysics law
explains this motion?
Solution : The ball’ s motion is explained b y Newton’ s law of gr avitation , which
sa ys that objects are pulled toward the Earth b y gr avity . When you throw the
ball up, gr avity pulls it back down, following a predictable path. This is a basic
rule of ph ysics that governs falling objects.
1
2 Ph ysics and Mathematics
Ph ysics and mathematics go hand in hand. Mathematics is lik e a language that
mak es it easier to describe the rules of nature. F or example, instead of sa ying,
”The force between two objects depends on their masses and the distance be-
tween them,” we can write a simple equation:
F ?
m
1
m
2
r
2
This equation sa ys the force (F ) is proportional t o the product of the masses
(m
1
m
2
) and inversely proportional to the square of the distance (r
2
). U sing math,
we can mak e predictions. F or instance, we can calculate the force between two
objects or how an object moves.
Mathematics is a tool, lik e a comfortable bus that helps us tr avel to our destination—
understanding nature. Without math, explaining ph ysics would be much harder ,
but the main goal is alwa ys to understand the natur al world, not just to do math.
K ey Idea : Mathematics is the language of ph ysics, making it easier to describe
and p redict natur al phenomena.
2.1 Solved Example: Using Mathematics in Ph ysics
Question : The force between t wo masses of 5 kg and 10 kg, separ ated b y 2 m, is
given b yF =
Gm
1
m
2
r
2
, whereG = 6.67×10
-11
N· m
2
/ kg
2
. Calculate the force.
Solution :
F =
(6.67×10
-11
)×5×10
2
2
=
6.67×10
-11
×50
4
=
3.335×10
-9
4
= 8.34×10
-10
N
The force is 8.34×10
-10
N.
3 Units
Ph ysics involves measuring things lik e length, mass, or time. T o measure an y-
thing, we need a standard unit. F or example, to know how much heavier an
elephant is compared to a goat, we choose a unit of mass (lik e a kilogr am). If
an elephant is 2000 k g and a goat is 50 k g, the elephant is 2000÷ 50 = 40 times
heavier .
A measurement has two parts: a number (how man y times the unit) and the unit
itself. F or example, ”3 meters” means 3 times the unit of length called a meter .
2
3.1 Who Decides Units?
Units need to be the same worldwide so everyone can understand measure-
ments. An international group called the Gener al Confer ence on W eights and
Measur es (CGPM) decides the standard units. These are published and used glob-
ally .
3.2 Fundamental and Derived Units
Not all quantities need their own unit. W e choose a few fundamental quantities
(lik e length, mass, and time) that are independent. Other quantities, lik e area
or speed, are derived from these. F or example: - Area : If the unit of length is a
meter , the unit of area is a square meter (m
2
). - Speed : If length is in meters and
time is in seconds, speed is in meters per second (m/ s).
There are seven fundamental quantities in the SI system (International S ystem
of Units), widely used around the world. They are listed below:
T able 1: Fundamental Quantities and SI Units
Quantity Unit Name S ymbol
Length metre m
Mass kilogr am k g
Time second s
Electric Current ampere A
Thermodynamic T emper ature k elvin K
Amount of Substance mole mol
Luminous Intensity candela c d
Two additional units are: - Plane angle : r adian (r ad) - Solid angle : ster adian
(sr)
3.3 SI Prefixes
Ph ysical quantities can be very large or very small. F or example, the distance
between stars is huge, while the size of an atom is tin y . T o handle this, we use
prefixes with SI units, lik e kilo (k) for 1000 or milli (m) for 1/1000. Here are some
common prefixes:
3.4 Solved Example: Using Units
Question : A car tr avels 150 km in 2 h. Calculate its speed in m/ s.
Solution :
Speed =
Distance
Time
3
T able 2: SI Prefixes
Power of 10 Prefix S ymbol
10
9
giga G
10
6
mega M
10
3
kilo k
10
-3
milli m
10
-6
micro µ
10
-9
nano n
Convert distance to meters: 150 km = 150× 1000 = 150,000 m. Convert time to
seconds: 2 h = 2×3600 = 7200 s.
Speed =
150,000
7200
= 20.83 m/ s
The speed is approximately 20.83 m/ s.
4 Definitions of Base Units
SI base units are defined using universal constants to ensure they are the same
everywhere and easy to use. Here are the definitions in simple terms (as of 2019):
- Second (s) : Defined using the frequency of a specific energy tr ansition in a cae-
sium atom, set to exactly 9,192,631,770 cycles. - Metre (m) : Defined so the speed
of light in a vacuum is exactly 299,792,458 meters per second. - Kilogr am (k g) :
Defined using Planck’ s constant, set to 6.62607015×10
-34
kg· m
2
/ s. - Ampere (A) :
Defined using the elementary charge, set to 1.602176634× 10
-19
C. - K elvin (K) :
Defined using the Boltzmann constant, set to 1.380649× 10
-23
J/ K. - Mole (mol) :
Defined as exactly 6.02214076×10
23
particles, called the A vogadro number . - Can-
dela (cd) : Defined using the luminous efficacy of light at a specific frequency ,
set to 683 lumens per watt.
K ey Idea : These definitions use fixed universal constants, making units consis-
tent and reproducible worldwide.
4.1 Solved Example: Applying Base Units
Question : A light beam tr avels 600.000 m in 2 s. Calculate the speed of light and
compare it to the defined value.
Solution :
Speed =
Distance
Time
=
600,000
2
= 300,000 m/ s
The defined speed of light is 299,792,458 m/s, so our calculated value is very close,
showing the meter and second definitions are consistent.
4
Page 5


1 What is Ph ysics?
Ph ysics is the study of how the world around us works. Nature is full of fasci-
nating things lik e the wind blowing, the sun shining, the planets moving, and
even how our bodies function. These are all called phenomena . Ph ysics helps
us understand these phenomena b y finding the basic rules, or laws , that govern
them.
F o r example, wh y does an apple fall from a tree? Wh y does the moon orbit the
Earth? These events follow rules lik e Newton’ s laws of motion and gr avitation.
B y discovering these rules, ph ysicists explain wh y things happen the wa y they
do. Ph ysics applies to everything, from tin y atoms to huge galaxies, and even
helps in fields lik e biology and medicine.
Think of ph ysics as a game where nature is the pla yer , and we are observers
trying to figure out the rules b y watching what happens. Sometimes, we guess a
rule, but new observations might show it’ s wrong, so we update it. Great scien-
tists lik e Newton and Einstein became famous b y guessing rules that explained
what t hey saw .
K ey Idea : Ph ysics is real because it studies nature directly . No one mak es up the
rules; we discover them through observation and experiments.
1.1 Solved Example: Understanding Phenomena
Question : A ball is thrown upward and comes back down. Which ph ysics law
explains this motion?
Solution : The ball’ s motion is explained b y Newton’ s law of gr avitation , which
sa ys that objects are pulled toward the Earth b y gr avity . When you throw the
ball up, gr avity pulls it back down, following a predictable path. This is a basic
rule of ph ysics that governs falling objects.
1
2 Ph ysics and Mathematics
Ph ysics and mathematics go hand in hand. Mathematics is lik e a language that
mak es it easier to describe the rules of nature. F or example, instead of sa ying,
”The force between two objects depends on their masses and the distance be-
tween them,” we can write a simple equation:
F ?
m
1
m
2
r
2
This equation sa ys the force (F ) is proportional t o the product of the masses
(m
1
m
2
) and inversely proportional to the square of the distance (r
2
). U sing math,
we can mak e predictions. F or instance, we can calculate the force between two
objects or how an object moves.
Mathematics is a tool, lik e a comfortable bus that helps us tr avel to our destination—
understanding nature. Without math, explaining ph ysics would be much harder ,
but the main goal is alwa ys to understand the natur al world, not just to do math.
K ey Idea : Mathematics is the language of ph ysics, making it easier to describe
and p redict natur al phenomena.
2.1 Solved Example: Using Mathematics in Ph ysics
Question : The force between t wo masses of 5 kg and 10 kg, separ ated b y 2 m, is
given b yF =
Gm
1
m
2
r
2
, whereG = 6.67×10
-11
N· m
2
/ kg
2
. Calculate the force.
Solution :
F =
(6.67×10
-11
)×5×10
2
2
=
6.67×10
-11
×50
4
=
3.335×10
-9
4
= 8.34×10
-10
N
The force is 8.34×10
-10
N.
3 Units
Ph ysics involves measuring things lik e length, mass, or time. T o measure an y-
thing, we need a standard unit. F or example, to know how much heavier an
elephant is compared to a goat, we choose a unit of mass (lik e a kilogr am). If
an elephant is 2000 k g and a goat is 50 k g, the elephant is 2000÷ 50 = 40 times
heavier .
A measurement has two parts: a number (how man y times the unit) and the unit
itself. F or example, ”3 meters” means 3 times the unit of length called a meter .
2
3.1 Who Decides Units?
Units need to be the same worldwide so everyone can understand measure-
ments. An international group called the Gener al Confer ence on W eights and
Measur es (CGPM) decides the standard units. These are published and used glob-
ally .
3.2 Fundamental and Derived Units
Not all quantities need their own unit. W e choose a few fundamental quantities
(lik e length, mass, and time) that are independent. Other quantities, lik e area
or speed, are derived from these. F or example: - Area : If the unit of length is a
meter , the unit of area is a square meter (m
2
). - Speed : If length is in meters and
time is in seconds, speed is in meters per second (m/ s).
There are seven fundamental quantities in the SI system (International S ystem
of Units), widely used around the world. They are listed below:
T able 1: Fundamental Quantities and SI Units
Quantity Unit Name S ymbol
Length metre m
Mass kilogr am k g
Time second s
Electric Current ampere A
Thermodynamic T emper ature k elvin K
Amount of Substance mole mol
Luminous Intensity candela c d
Two additional units are: - Plane angle : r adian (r ad) - Solid angle : ster adian
(sr)
3.3 SI Prefixes
Ph ysical quantities can be very large or very small. F or example, the distance
between stars is huge, while the size of an atom is tin y . T o handle this, we use
prefixes with SI units, lik e kilo (k) for 1000 or milli (m) for 1/1000. Here are some
common prefixes:
3.4 Solved Example: Using Units
Question : A car tr avels 150 km in 2 h. Calculate its speed in m/ s.
Solution :
Speed =
Distance
Time
3
T able 2: SI Prefixes
Power of 10 Prefix S ymbol
10
9
giga G
10
6
mega M
10
3
kilo k
10
-3
milli m
10
-6
micro µ
10
-9
nano n
Convert distance to meters: 150 km = 150× 1000 = 150,000 m. Convert time to
seconds: 2 h = 2×3600 = 7200 s.
Speed =
150,000
7200
= 20.83 m/ s
The speed is approximately 20.83 m/ s.
4 Definitions of Base Units
SI base units are defined using universal constants to ensure they are the same
everywhere and easy to use. Here are the definitions in simple terms (as of 2019):
- Second (s) : Defined using the frequency of a specific energy tr ansition in a cae-
sium atom, set to exactly 9,192,631,770 cycles. - Metre (m) : Defined so the speed
of light in a vacuum is exactly 299,792,458 meters per second. - Kilogr am (k g) :
Defined using Planck’ s constant, set to 6.62607015×10
-34
kg· m
2
/ s. - Ampere (A) :
Defined using the elementary charge, set to 1.602176634× 10
-19
C. - K elvin (K) :
Defined using the Boltzmann constant, set to 1.380649× 10
-23
J/ K. - Mole (mol) :
Defined as exactly 6.02214076×10
23
particles, called the A vogadro number . - Can-
dela (cd) : Defined using the luminous efficacy of light at a specific frequency ,
set to 683 lumens per watt.
K ey Idea : These definitions use fixed universal constants, making units consis-
tent and reproducible worldwide.
4.1 Solved Example: Applying Base Units
Question : A light beam tr avels 600.000 m in 2 s. Calculate the speed of light and
compare it to the defined value.
Solution :
Speed =
Distance
Time
=
600,000
2
= 300,000 m/ s
The defined speed of light is 299,792,458 m/s, so our calculated value is very close,
showing the meter and second definitions are consistent.
4
5 Dimensions
Every ph ysical quantity can be expressed using the seven base quantities (length,
mass, time, etc.). The dimensional formula shows how a quantity depends on
these base quantities. F or example, force is defined as:
F orce = mass× acceler ation, acceler ation =
velocity
time
, velocity =
length
time
So:
F orce = mass×
length/time
time
= mass× length× time
-2
Using symbols (M for mass, L for length, T for time), the dimensional formula for
force is MLT
- 2
. This means force has dimension 1 in mass, 1 in length, and -2 in
time.
5.1 Solved Example: Dimensional F ormula
Question : Find the dimensional formula for kinetic energy , given b yKE =
1
2
mv
2
.
Solution :
Kinetic energy = mass×( velocity)
2
V elocity =
length
time
= L/ T, so:
[KE] = M×
(
L
T
)
2
= M×
L
2
T
2
= ML
2
T
- 2
The d imensional formula is ML
2
T
- 2
.
6 Uses of Dimensions
Dimensions help in three main wa ys:
6.1 A . Checking Equations (Homogeneity)
An equation is correct only if all terms have the same dimensions. This is called
the principle of homogeneity . F or example, check the equation for distance tr av-
eled:
x = ut+
1
2
at
2
-[x] = L (distance is length). -[ut] =
L
T
× T = L (velocity × time). -
[
1
2
at
2
]
=
L
T
2
× T
2
= L
(acceler ation × time²).
All terms have dimension L, so the equation is dimensionally correct.
5