Download 9th Class Physics Notes (Unit # 2) for Federal Board (FBISE) Islamabad
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SHORT QUESTIONS
[Important] Question: Differentiate between followings:
Rest and Motion:
 A body is said
to be at rest, if it does not change its position with respect to
its surroundings.
 A body is said
to be in motion, if it changes its position with respect to its
surroundings.
Circular Motion and Rotatory Motion:
 Any turning as
if on an axis is rotatory motion.
 Any rotatory
motion where the radius of gyration length and axis of rotation are fixed
is circular motion.
 So the main
difference is that there is no fixed axis and radius restriction for
rotatory motion, but there is for circular motion.
Scalars and Vectors:
·
A scalar quantity is
described completely by its magnitude only. For example mass, length, time,
speed, volume, work, energy, density, power, electric charge, pressure, area,
temperature etc.
·
A vector quantity is
described completely by magnitude and direction. For example velocity,
displacement, force, momentum, torque, weight, electric potential etc.
Distance and Displacement:
Distance
Displacement
·
Length of a path between two
points is called the distance between those points.
·
Distance is a scalar quantity
·
Distance is denoted by “S” and S =
vt.
·
Its unit is metre (m)
·
Displacement is the shortest
distance between two points which has magnitude and direction.
·
Displacement is a vector quantity.
·
Displace is denoted by “d” and d =
vt
·
Its unit is metre (m)
Speed and Velocity:
Speed
Velocity
The distance covered an object in unit
time is called its speed
Distance
covered
Speed = 
Time
taken
Distance = speed x time
S = vt
The rate of displacement of a body is
called its velocity.
Displacement
Velocity = 
Time
taken
v = d / t
d = vt
Speed is scalar quantity
Velocity is vector quantity
Its SI unit is meter per second (ms^{1})
Its SI unit is meter per second (ms^{1})
Linear Motion and Random Motion:
·
Straight line motion of a body is
known as linear motion. For example a car is moving on straight and level road
or aero plane flying straight in air.
·
The disordered or irregular motion
of an object is called random motion. For example motion of insects and birds.
[Very Important] Question: What is Gyration Length?
A length that represents the distance in a
rotating system between the point about which it is rotating and the point to
or from which a transfer of energy has the maximum effect.
Question:
Define Acceleration:
Acceleration is defined as the rate of
change of velocity of a body.
Change
in velocity
Acceleration = 
Time
taken
V_{f}V_{i}
a = 
t
The SI unit of acceleration is meter per
second per second (ms^{2})
[Important] Question: Can a body moving at a constant
speed have acceleration?
Yes, when a body is moving with constant
speed, the body can have acceleration if its direction changes. For example if
the body is moving along a circle with constant speed. It will have
acceleration due to the change of direction at very instant.
[Important] Question: How do riders in a Ferris wheel possess
translatory motion but not circular motion?
Riders in a Ferris wheel possess
translatory motion because their motion is in a circle without rotation.
Question:
How can vector quantities be represented graphically?
To differentiate a vector from a scalar
quantity, we generally se bold letters to represent vector quantities, such as
F, a, d or a bar or arrow over their symbols such as F, a, d or F.
Graphical representation:
A straight line is drawn with an arrow head
at one end. The length of the line, according to some suitable scale,
represents the magnitude and the arrow head gives the direction of the vector.
[Important] Question: Why vector quantities cannot be
added and subtracted like scalar quantities?
The scalar quantities obey the rules of
arithmetic and ordinary algebra because scalar quantities have no direction.
Since vectors have magnitude as well as direction, so vectors obey the special
rules of vector algebra therefore vectors are added by head to tail rule.
(Vector Algebra)
Question:
Which from following can be obtained from speedtime graph. Initial Speed,
Final Speed, Distance covered in time and Acceleration of motion.
All above factors can be obtained from
speedtime graph.
>>
Question: Define Kinematics.
It is the study of motion of an object
without discussing the cause of motion.
>>
Question: Define Surroundings.
Surroundings are the places in its neighborhood
where various objects are present.
[Important] >> Question: List types of motion
i)
Translatory motion (Linear, Random
and Circular)
ii)
Rotatory motion
iii)
Vibratory motion
[Very Important] >> Question: Define Translatory motion
and its types.
In translatory motion, body moves along a
line without any rotation. The line may be straight or curved. It has following
types:
Linear Motion:
Straight line motion of a body is called
linear motion. For example car moving in straight line.
Circular Motion:
The motion of an object in a circular path
is called circular motion. For example a stone tied at one end of string and
whirled.
Random Motion:
The disordered or irregular motion is
called random motion. For example motion of birds and insects.
[Important] >> Question: Define Rotatory Motion.
The spinning motion of a body about its
axis is called rotary motion. For example the top spins about its axis passing
through it and thus it possess rotatory motion.
[Important] >> Question: Define Vibratory motion.
To and fro motion of a body about its mean
position is called vibratory motion. For example motion of a baby in swing.
>>
Question: Mention type of motion in followings.
A ball moving vertically upward
Linear motion
A child moving down a slide
Linear motion
Movement of a player in a football ground
Random motion
The flight of a butterfly
Random motion
An athlete running in a circular track
Circular motion
The motion of a wheel
Circular motion
The motion of a cradle
Vibratory motion
[Important] >> Question: Define Position.
The term position describes the location of
a place or a point with respect to some reference point called origin.
>>
Question: Which is fastest animal on the earth?
Falcon can fly at a speed of 200 kmh^{1}.
While Cheetah can run at a speed of 70kmh^{1}
[Very Important] >> Question: What is LIDAR gun?
A LIDAR gun is light detection and ranging
speed gun. It uses the time taken by laser pulse to make a series of
measurements of a vehicle’s distance from the gun. The data is then used to
calculate the vehicle’s speed.
[Very Important] >> Question: Define Uniform, Variable
and Average Speed.
 A body has uniform
speed if it covered equal distances in equal intervals of time however
short the interval may be.
 If a body
covers unequal distances in equal interval of time, however small the
intervals may be, the speed of the body is said to be variable.
 The ratio
between distance and total time taken is known as average speed.
[Very Important] >> Question: Define Uniform Velocity,
Variable Velocity and Average Velocity?
 A body has uniform
velocity if it covers equal displacement in equal intervals of time
however short the interval may be.
 If speed or
direction changes with time then the velocity is said to be variable.
 The ratio
between displacement and time is known as average velocity.
[Very Important] >> Question: Define Uniform
Acceleration, Variable Acceleration and Positive & Negative Acceleration.
 A body has uniform
acceleration if it has equal changes in velocity in equal intervals
of time however short the interval may be.
 A body has variable
acceleration if it has not equal changes in velocity in equal
intervals of time however short the interval may be.
 Acceleration
of a body is positive when its velocity is increasing and negative
when its velocity is decreasing.
[Important] >> Question: Define Graph, Variables,
Independent quantity and dependent quantity.
 Graph is a
pictorial way of presenting information about the relation between various
quantities.
 The quantities
between which a graph is plotted are called variables.
 One of the
quantities is called independent quantity.
 The value of
which varies with the independent quantity is called the dependent quantity.
>>
Question: What is the purpose of distance time graph?
It is useful to represent the motion of
objects using graphs.
>>
Question: Define Gravitational Acceleration.
The acceleration of freely falling bodies
is called gravitational acceleration. It is denoted by g. Its value is
approximately 10ms^{2}.
[Very Important] >> Write equation of motion under
gravity.
i) V_{f}
= V_{i} + gt ii) h = V_{i}t + ½ gt^{2} iii) 2gh
= V_{f}^{2} – V_{i}^{2}
LONG QUESTIONS
[Very Important] >>
Question: Derive the First Equation of Motion?
Let a car is moving with initial velocity
(v_{i}). After time (t) its velocity becomes (v_{f}). As the
car is moving with uniform acceleration therefore its acceleration (a) will be
equal to the average acceleration (a_{av}):
Change
in Velocity
a = 
Total Time
V_{f} – V_{i}
a = 
t
at = V_{f}
– V_{i}
at + V_{i} = V_{f}
OR
V_{f} = V_{i}
+ at
Second Method:
[Very Important] >>
Question: Derive the Second Equation of Motion?
A body is moving with initial Velocity (V_{i})
and after time (t) its velocity becomes (V_{f}). Then to calculate the
total distance (S) covered in time (t):
Distance = Average Velocity x Time
S = V_{av} x t
 (i)
We know that
V_{i}
+ V_{f}
V_{av} = 
2
So, Putting this value in equation (i)
V_{i}
+ V_{f}
S =  x t
2
And we know that V_{f} = V_{i}
+ at
So,
V_{i}
+ V_{i} + at
S =  x t
2
2V_{i}
+ at
S =  x t
2
2V_{i}t
+ at^{2}
S = 
2
2V_{i}t at^{2}
S =  + 
2 2
1
S = V_{i}t +  at^{2}
2
Second Method:
[Very Important] >>
Question: Derive the Third Equation of Motion?
A body is moving with initial velocity (v_{i})
and after time (t) its velocity becomes (v_{f}) then distance covered
by it is given by:
(V_{i}
+ V_{f})
S =  x t 
(i)
2
We know that
V_{f} = V_{i}
+ at
OR
V_{f}
– V_{i}
t = 
a
Putting the value of t in equation (i)
(V_{i} + V_{f}) (V_{f}
 V_{i})
S = 
x 
2 a
2aS = (V_{i}
+ V_{f}) x (V_{f}  V_{i})
2as = Vf^{2} – Vi^{2}
Second Method:
=*=*=*=*=
SHORT QUESTIONS
[Important] Question: Differentiate between followings:
Rest and Motion:
 A body is said
to be at rest, if it does not change its position with respect to
its surroundings.
 A body is said
to be in motion, if it changes its position with respect to its
surroundings.
Circular Motion and Rotatory Motion:
 Any turning as
if on an axis is rotatory motion.
 Any rotatory
motion where the radius of gyration length and axis of rotation are fixed
is circular motion.
 So the main
difference is that there is no fixed axis and radius restriction for
rotatory motion, but there is for circular motion.
Scalars and Vectors:
·
A scalar quantity is
described completely by its magnitude only. For example mass, length, time,
speed, volume, work, energy, density, power, electric charge, pressure, area,
temperature etc.
·
A vector quantity is
described completely by magnitude and direction. For example velocity,
displacement, force, momentum, torque, weight, electric potential etc.
Distance and Displacement:
Distance

Displacement

·
Length of a path between two
points is called the distance between those points.
·
Distance is a scalar quantity
·
Distance is denoted by “S” and S =
vt.
·
Its unit is metre (m)

·
Displacement is the shortest
distance between two points which has magnitude and direction.
·
Displacement is a vector quantity.
·
Displace is denoted by “d” and d =
vt
·
Its unit is metre (m)

Speed and Velocity:
Speed

Velocity

The distance covered an object in unit
time is called its speed
Distance
covered
Speed = 
Time
taken
Distance = speed x time
S = vt

The rate of displacement of a body is
called its velocity.
Displacement
Velocity = 
Time
taken
v = d / t
d = vt

Speed is scalar quantity

Velocity is vector quantity

Its SI unit is meter per second (ms^{1})

Its SI unit is meter per second (ms^{1})

Linear Motion and Random Motion:
·
Straight line motion of a body is
known as linear motion. For example a car is moving on straight and level road
or aero plane flying straight in air.
·
The disordered or irregular motion
of an object is called random motion. For example motion of insects and birds.
[Very Important] Question: What is Gyration Length?
A length that represents the distance in a
rotating system between the point about which it is rotating and the point to
or from which a transfer of energy has the maximum effect.
Question:
Define Acceleration:
Acceleration is defined as the rate of
change of velocity of a body.
Change
in velocity
Acceleration = 
Time
taken
V_{f}V_{i}
a = 
t
The SI unit of acceleration is meter per
second per second (ms^{2})
[Important] Question: Can a body moving at a constant
speed have acceleration?
Yes, when a body is moving with constant
speed, the body can have acceleration if its direction changes. For example if
the body is moving along a circle with constant speed. It will have
acceleration due to the change of direction at very instant.
[Important] Question: How do riders in a Ferris wheel possess
translatory motion but not circular motion?
Riders in a Ferris wheel possess
translatory motion because their motion is in a circle without rotation.
Question:
How can vector quantities be represented graphically?
To differentiate a vector from a scalar
quantity, we generally se bold letters to represent vector quantities, such as
F, a, d or a bar or arrow over their symbols such as F, a, d or F.
Graphical representation:
A straight line is drawn with an arrow head
at one end. The length of the line, according to some suitable scale,
represents the magnitude and the arrow head gives the direction of the vector.
[Important] Question: Why vector quantities cannot be
added and subtracted like scalar quantities?
The scalar quantities obey the rules of
arithmetic and ordinary algebra because scalar quantities have no direction.
Since vectors have magnitude as well as direction, so vectors obey the special
rules of vector algebra therefore vectors are added by head to tail rule.
(Vector Algebra)
Question:
Which from following can be obtained from speedtime graph. Initial Speed,
Final Speed, Distance covered in time and Acceleration of motion.
All above factors can be obtained from
speedtime graph.
>>
Question: Define Kinematics.
It is the study of motion of an object
without discussing the cause of motion.
>>
Question: Define Surroundings.
Surroundings are the places in its neighborhood
where various objects are present.
[Important] >> Question: List types of motion
i)
Translatory motion (Linear, Random
and Circular)
ii)
Rotatory motion
iii)
Vibratory motion
[Very Important] >> Question: Define Translatory motion
and its types.
In translatory motion, body moves along a
line without any rotation. The line may be straight or curved. It has following
types:
Linear Motion:
Straight line motion of a body is called
linear motion. For example car moving in straight line.
Circular Motion:
The motion of an object in a circular path
is called circular motion. For example a stone tied at one end of string and
whirled.
Random Motion:
The disordered or irregular motion is
called random motion. For example motion of birds and insects.
[Important] >> Question: Define Rotatory Motion.
The spinning motion of a body about its
axis is called rotary motion. For example the top spins about its axis passing
through it and thus it possess rotatory motion.
[Important] >> Question: Define Vibratory motion.
To and fro motion of a body about its mean
position is called vibratory motion. For example motion of a baby in swing.
>>
Question: Mention type of motion in followings.
A ball moving vertically upward

Linear motion

A child moving down a slide

Linear motion

Movement of a player in a football ground

Random motion

The flight of a butterfly

Random motion

An athlete running in a circular track

Circular motion

The motion of a wheel

Circular motion

The motion of a cradle

Vibratory motion

[Important] >> Question: Define Position.
The term position describes the location of
a place or a point with respect to some reference point called origin.
>>
Question: Which is fastest animal on the earth?
Falcon can fly at a speed of 200 kmh^{1}.
While Cheetah can run at a speed of 70kmh^{1}
[Very Important] >> Question: What is LIDAR gun?
A LIDAR gun is light detection and ranging
speed gun. It uses the time taken by laser pulse to make a series of
measurements of a vehicle’s distance from the gun. The data is then used to
calculate the vehicle’s speed.
[Very Important] >> Question: Define Uniform, Variable
and Average Speed.
 A body has uniform
speed if it covered equal distances in equal intervals of time however
short the interval may be.
 If a body
covers unequal distances in equal interval of time, however small the
intervals may be, the speed of the body is said to be variable.
 The ratio
between distance and total time taken is known as average speed.
[Very Important] >> Question: Define Uniform Velocity,
Variable Velocity and Average Velocity?
 A body has uniform
velocity if it covers equal displacement in equal intervals of time
however short the interval may be.
 If speed or
direction changes with time then the velocity is said to be variable.
 The ratio
between displacement and time is known as average velocity.
[Very Important] >> Question: Define Uniform
Acceleration, Variable Acceleration and Positive & Negative Acceleration.
 A body has uniform
acceleration if it has equal changes in velocity in equal intervals
of time however short the interval may be.
 A body has variable
acceleration if it has not equal changes in velocity in equal
intervals of time however short the interval may be.
 Acceleration
of a body is positive when its velocity is increasing and negative
when its velocity is decreasing.
[Important] >> Question: Define Graph, Variables,
Independent quantity and dependent quantity.
 Graph is a
pictorial way of presenting information about the relation between various
quantities.
 The quantities
between which a graph is plotted are called variables.
 One of the
quantities is called independent quantity.
 The value of
which varies with the independent quantity is called the dependent quantity.
>>
Question: What is the purpose of distance time graph?
It is useful to represent the motion of
objects using graphs.
>>
Question: Define Gravitational Acceleration.
The acceleration of freely falling bodies
is called gravitational acceleration. It is denoted by g. Its value is
approximately 10ms^{2}.
[Very Important] >> Write equation of motion under
gravity.
i) V_{f}
= V_{i} + gt ii) h = V_{i}t + ½ gt^{2} iii) 2gh
= V_{f}^{2} – V_{i}^{2}
LONG QUESTIONS
[Very Important] >>
Question: Derive the First Equation of Motion?
Let a car is moving with initial velocity
(v_{i}). After time (t) its velocity becomes (v_{f}). As the
car is moving with uniform acceleration therefore its acceleration (a) will be
equal to the average acceleration (a_{av}):
Change
in Velocity
a = 
Total Time
V_{f} – V_{i}
a = 
t
at = V_{f}
– V_{i}
at + V_{i} = V_{f}
OR
V_{f} = V_{i}
+ at
Second Method:
[Very Important] >>
Question: Derive the Second Equation of Motion?
A body is moving with initial Velocity (V_{i})
and after time (t) its velocity becomes (V_{f}). Then to calculate the
total distance (S) covered in time (t):
Distance = Average Velocity x Time
S = V_{av} x t
 (i)
We know that
V_{i}
+ V_{f}
V_{av} = 
2
So, Putting this value in equation (i)
V_{i}
+ V_{f}
S =  x t
2
And we know that V_{f} = V_{i}
+ at
So,
V_{i}
+ V_{i} + at
S =  x t
2
2V_{i}
+ at
S =  x t
2
2V_{i}t
+ at^{2}
S = 
2
2V_{i}t at^{2}
S =  + 
2 2
1
S = V_{i}t +  at^{2}
2
Second Method:
[Very Important] >>
Question: Derive the Third Equation of Motion?
A body is moving with initial velocity (v_{i})
and after time (t) its velocity becomes (v_{f}) then distance covered
by it is given by:
(V_{i}
+ V_{f})
S =  x t 
(i)
2
We know that
V_{f} = V_{i}
+ at
OR
V_{f}
– V_{i}
t = 
a
Putting the value of t in equation (i)
(V_{i} + V_{f}) (V_{f}
 V_{i})
S = 
x 
2 a
2aS = (V_{i}
+ V_{f}) x (V_{f}  V_{i})
2as = Vf^{2} – Vi^{2}
Second Method:
=*=*=*=*=
COMMENTS