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1. CLASS 9
PHYSICS
CHAPTER 1
MOTION

2. Introduction
❏ In our daily life, we see some object at rest
and other in Motion.
❏ 🐦 Bird's fly, fishes swim, blood flows
through vein and arteries and car moves,
these are some examples of the State of
Motion.
❏ Motion is a state of body if it's position
changes with respect to the Time.
❏ There are also situation where the Motion
is inferred through indirect evidences.
❏ An object may appear to be moving for
one person and stationary for some other.
❏ In this chapter through the lecture and
slide we will study motion in straight line
and at last we shall discuss the circular
motion.
This is a reference image to show Motion.

3. Physical Quantity
Scalar Quantity
The quantity having only magnitude it is said to
be Scalar Quantity.
❏ Mass
❏ Distance
❏ Speed
❏ Time
❏ Temperature
❏ Boiling point
❏ Density
❏ Work
❏ Energy, etc.
Vector Quantity
The quantity having both magnitude as well as
the direction it is said to be Vector Quantity.
❏ Displacement
❏ Velocity
❏ Acceleration
❏ Force
❏ Momentum
❏ Torque, etc.

4. To describe the position of an object we
needto specify reference point called the
origin.

5. Motion along a straight line
❏ The simplest type of Motion is the Motion along a straight line.
❏ For Example- If a object start it's journey he travelled from O to C, then C to
B, then B to A.
❏ The total path covered by a an object is called the total distance covered.
❏ The shortest distance between any two positions.
❏ In next slide we will go through difference between Total dis covered and
Displacement.

6. Difference between the total distance and
Displacement
Total distance covered
❏ Total Distance
❏ The value of Distance covered is only
positive.
❏ It can not be zero.
❏ It is a Scalars Quantity.
Displacement
❏ Shortest Distance
❏ The value of Displacement may be
positive or negative.
❏ It can be zero.
❏ It is a Vector Quantity.

7. Uniform Motion And Non Uniform Motion
Uniform Motion
❏ If the object covers equal distance in equal
interval of time, It is said to be in Uniform
Motion.
❏ For example :-
❏ If a object covers 50 km in first hour and
again 50 km in next hour, then it is a
Uniform Motion.
Non Uniform Motion
❏ If a object covers unequal distance in
equal interval of time, it is said to be Non -
Uniform Motion.
❏ For example :-
❏ If a object covers 50 km in first hour and
again 30 km in next hour, then it a Non
Uniform Motion.

8. Measuring the Rate of Motion
❏ The ways of measuring the rate of motion
of an object is to find out the distance
travelled by the object in unit time. This
quantity is referred as speed.
❏ The SI unit of speed is metre per second.
❏ This is represented by the symbol m/sec.
❏ The other units are cm/sec, km/h.
❏ To specify the speed of an object, we
require only it's magnitude.
❏ The speed of object need not to be
constant.
❏ in most cases object will be in non uniform
motion.
❏ Therefore we describe the rate of motion
of such objecys in terms of average
speed.
❏ The average speed of an object is
obtained by dividing the total distance
travelled by the total time taken i.e.

9. Speed With Direction
❏ The rate of motion of an object can be
more comprehensive if we specify its
direction of motion along with speed.
❏ The quantity that specifies both this aspect
is called velocity.
❏ Velocity is the speed of an object moving
in a definite direction.
❏ The velocity of an object can be uniform or
variable it can be changed by changing
the object speed direction of the motion or
both.
❏ When an object is moving in a straight line
at a variable speed we can express the
magnitude of its rate of motion in terms of
average velocity.
❏ It is calculated in the same way as we
calculate the average speed.
❏ In this case the velocity of the object is
changing at a uniform rate, then average
velocity is given by arithmetic mean of
initial velocity and final velocity for a given
period of time that is,

10. Rate of Change of Velocity
❏ During uniform motion of an object along a
straight line, the velocity remains constant
with time. In this case the change in
velocity of object for any time interval is
zero.
❏ In non uniform motion, velocity varies with
time. It has different value at different
instant and different points of the path.
❏ Thus, change in velocity of object during
any time interval is not zero.
❏ At this time we introduce a new physical
quantity that is acceleration.
❏ Acceleration is the measure of change in
the velocity of an object per unit time that
is,

12. Graphical Representation of Motion
Distance - Time Graph
❏ The change in the position of an object
which time can be represented on the
distance time graph adopting a convenient
scale of choice.
❏ In this graph, time is taken along the x axis
and distance taken along the y axis.
❏ Distance time graph can be employed
under the various conditions where objects
move with uniform speed, non uniform
speed, remains at rest, etc.

14. Graphical Representation of Motion
Velocity - Time Graph
❏ The variation in velocity with time for an
object moving in a straight line can be
represented by a velocity time graph.
❏ In this graph, time is represented along the
x-axis and the velocity is represented
along the y axis.
❏ If the object moves at uniform velocity the
height of its velocity time graph will not
change with time. It will be straight line
parallel to x axis shown in fig. 8.5

18. Equation of Motion by Graphical Method

26. Uniform Circular Motion
❏ When the velocity of an object changes we
say that object is accelerating. the change
in velocity could be due to the change in
its magnitude or the direction of the motion
or the both.
❏

27. THANK YOU