The document discusses various concepts of motion in physics, defining key terms such as distance, displacement, speed, velocity, and acceleration. It explains how to represent motion graphically through distance-time, displacement-time, velocity-time, and acceleration-time graphs, detailing their characteristics and implications. Additionally, it introduces equations of motion and circular motion, emphasizing the changes in an object's position over time and the mathematical relationships involved.

1. Life is a full circle, widening until it joins the circle
motions of the infinite

2. What is Motion
Motion :- It is the change in position of a body with time. Motion can be
described in terms of the distance moved or the displacement.
Concept :- In physics, motion is a change in position of an object with
respect to time. Motion is typically described in terms
of displacement, distance, velocity, acceleration, time and speed. Motion
of a body is observed by attaching a frame of reference to an observer
and measuring the change in position of the body relative to that frame.
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4. DISTANCE
Distance moved :- It is the actual length of the path travelled by a body.
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Total Distance
covered in ONE
LAP = 400m
Starting & Ending
point

5. DISPLACEMENT
Displacement :- It is the length of the shortest path travelled by a body
from its initial position to its final position.
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5
Total
displacement in
ONE LAP = 0
Starting & ending
point

6. SPEED
Speed :- Speed of a body is the distance travelled by the body in unit
time.
Speed = Distance
Time
If a body travels a distance s in time t then its speed v is
v = s
t
The SI unit of speed is metre per second m/s or ms -1
Since speed has only magnitude it is a scalar quantity.
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7. VELOCITY
The rate of motion of a body is more meaningful if we specify its direction of
motion along with speed. The quantity which specifies both the direction of
motion and speed is velocity.
Velocity :- Velocity of a body is the displacement of the body per unit time.
Velocity = Displacement
Time taken
Since velocity has both magnitude and direction, it is a vector quantity.
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8. ACCELERATION
The quantity which specifies changes in velocity is acceleration.
Acceleration :- It is the change in velocity of a body per unit time. ( or
the rate of change of velocity.)
Acceleration = Change in velocity
Time
If the velocity of a body changes from initial value u to final value v in
time t, then acceleration a is
a = v - u
t .The SI unit of acceleration is ms - 2
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9. PLOTTING POINTS
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We already know how to plot points on a graph. So let`s recall them. Suppose I
want to plot points (3, 4) on a graph, it will be as follows :-
0
1
2 3 4 51
2
3
4
5
Y
X
Points to plot (3, 4)
X = 3
Y = 4
In this similar way, we can plot many other
points on a graph.

10. GRAPHS AND ITS
TYPES• A graph is a pictorial representation of observation. It consist of two
variables, one is independent variable and other is dependent variable.
• Independent variable is taken along X-axis and dependent variable is taken
along Y-axis.
• There are many types of graphs in physics, some of them are as follows :-
1. Distance time graph 2. Displacement time graph
3. Velocity time graph 4. Acceleration time graph
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11. DISTANCE TIME
GRAPHThe change in the position of a body with time can be represented on
the distance time graph. In this graph distance is taken on the Y – axis
and time is taken on the X – axis. The distance time graph for uniform
speed is a straight line ( linear ).
This is because in uniform speed a body travels equal distances in equal
intervals of time. We can determine the speed of the body from the
distance – time graph.
They are used to find speed or velocity of body.
The slope of it gives speed of body.
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There are 3–Types of distance time
graphs.1. When body is at rest – It`s a straight line parallel to time axis.
t
d
2. When body is mpving with uniform speed – when the body is moving with uniform speed
the graph is a straight line making an angle with the time axis and the slope of this graph
is given by - slope = Y2 – Y1 / X2 – X1 which is equal to speed.
t
d

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3. When a body is moving with Non uniform speed – The body covers unequal
distances in equal intervals of time.
t
d
t
ddecreasing
speed
increasing
speed
These curves are called parabola.
So, greater the angle, greater is the slope and greater is the speed

14. DISPLACEMENT TIME
GRAPH
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It is a vector quantity and it`s slope gives velocity.
There are 3-Types of displacement time graph, they are as follows :-
1. When body is at rest -
t
s Slope of this graph is 0.

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2. Body moving with uniform speed -
t
s Q1
Q2
A
B Where Q1 > Q2
Velocity of A > Velocity of B
3. Body moving with variable/non uniform velocity -
t
s velocity
increases s
velocity
decreases
t

16. VELOCITY TIME
GRAPH
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For a body moving in straight line, without changing it`s direction, velocity of
body becomes equal to it`s speed.
The slope of velocity time graph gives acceleration of body.
The area under this graph gives the value of distance travelled.
There are 3 different cases of this graph, which we have discussed next -

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CASE - I
If the body is moving with constant speed.
t
v Slope = 0
Acceleration = ms - 2
Constant speed – If the body moves with constant velocity/speed then graph is straight
line parallel to time axis and slpoe and acceleration will be 0.

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CASE - II
When a body is moving with uniformly changing speed -
a.) If speed increases uniformly.
v
t
This slope is known as positive slope and slope gives
uniform acceleration.
b.) If speed is decreasing uniformly -
v
t
The graph is straight line slope downwards. Hence, the slope is
negative. The slope of this graph gives retardation.
Area in both cases (a & b) gives distance travelled by body.

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CASE - III
Non uniformly changing speed.
a.) If speed increases non uniformly.
v
t
The graph is a curve moving upward. The slope of tangent
drawn at any point on curve is positive and is equal to
acceleration of body.
b.) If speed decreases non uniformly.
t
v The graph is a curve moving downwards and the slope of
tangent is negative and gives the value of retardation.

20. ACCELERATION TIME
GRAPH
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The graph is as shown below -
CASE - I
V
t
For a body at rest -
Acceleration is 0 for a body at
rest or when is moves with
uniform speed
CASE - II
For a body moving with uniform acceleration.
slope = 0
t
a
-a
slope = 0
In uniform acceleration the acceleration is constant and
does not change and hence the graph is straight line
parallel to time axis.

21. EQUATIONS OF MOTION BY
GRAPHICAL METHOD
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The motion of a body moving with uniform acceleration can be described
with the help of three equations called equations of motion.
The equations of motion are :-
i) v = u + at
ii) s = ut + ½ at2
iii) 2as = v2 – u2
Where u - is the initial velocity
v - is the final velocity
a - is acceleration
t - is the time
s - is the distance traveled

22. CIRCULAR
MOTION
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The motion of a body in a circular path is called circular motion.
Uniform circular motion :- If a body moves in a circular path with uniform
speed, its motion is called uniform circular motion.
Uniform circular motion is accelerated motion because in a circular motion a body
continuously changes its direction.
The circumference of a circle of radius r is given by 2πr. If a body takes time t to go once
around the circular path, then the velocity v is given by
v = 2πr
t

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Name – Mridul Verma
Class – 9 – A
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