THIS PPT IS BASED ON THE CHAPTER MOTION FOR CLASS 9

1. Science
project
work

2. MOTION
 Motion:
A body is said to be in motion
when its position changes continuously
with respect to a stationary object taken as
a reference point.
 Characteristic of Motion :
A common
characteristic of all moving object are they
change their position with respect to time.

3.  Examples of motion:
1. Swing
2. Merry go round
3. Pendulum of a clock
4. Hands of a watch

4.  If a body moves fairly fast, then its
movement can be observed easily. But
if a body moves very slowly, then it
become difficult to observe its
movement immediately.
 For example:
A watch had three hands
i.e. a second’s, minute’s & hour’s. The
speed of second’s is fast so, its motion
can be observed. But the minute’s &
hour’s hand is slow so, its motion
cannot be observed.

5.  Distance travelled:
The distance
travelled b a body is the actual
length of the path covered by a
moving body irrespective of the
direction in which the body travels.
It is a scalar quantity.

6.  When a body moves from one point
to another, the distance travelled
refers to the actual length of the
indirect path whereas displacement
refers to the straight line path
between the initial & the final
positions.
 Displacement:
The shortest distance
between the initial position & the final
position is known as its
displacement.
It is a vector quantity.

7.  Scalar quantity:
A physical quantity
having only magnitude is known as a
scalar quantity. A scalar quantity has
no direction.
 Vector quantity:
A physical quantity
having only magnitude as well as
direction is known as vector quantity.

8.  The distance travelled by a moving
body can't be zero but the final
displacement of a moving body can
be zero.
 Uniform Motion:
A body has a uniform
motion if it travels equal distances in
equal intervals of time.

9. GRAPH OF UNIFORM MOTION

10.  Non–Uniform Motion:
A body has a
non–uniform motion if it travels equal
distances in equal intervals. of time.

11.  Non-uniform motion is also called
accelerated motion.
 Speed:
Speed of a body is the distance
travelled by it per unit time.
Formula for speed is:
Speed = Distance travelled
Time taken
Where:
v = speed
s = distance travelled
and t = time taken

12.  Speed gives the idea how slow or fast the
body is moving.
 The SI unit of speed is meters per second.
 The small values of speed are expressed in
the unit of cm. per sec. To express high
speed values we use the unit of km. per hr.
 It is a scalar quantity because it has only
magnitude not specified direction.
 If we have to compare the speeds of a
number of bodies, then we must express
the speed of all of them in the same unit.

13.  Average speed:
The average sped of a
body is the total distance travelled by the
total time taken to cover this distance.
Formula for Average speed is:
Average speed = Total distance travelled
Total time taken
Where:
v = average speed
s = total distance travelled
and t = total time taken

14.  Speedometer:
An instrument for
measuring speed of the moving
vehicle.
 Odometer:
An instrument for
measuring distance travelled by the
vehicle.

15.  Uniform speed:
A body has a uniform
speed if it travels equal distances in
equal intervals of time.
 Velocity:
Velocity of a body is the
distance travelled by it per unit time in
a given direction.
Formula for Velocity is:
Velocity= Displacement
Time taken

16. v = s
t
Where:
v = velocity
s = displacement
and t = time taken
 The SI unit of velocity is meter per second.
 It is a vector quantity because is has
magnitude as well as direction.
 The direction of velocity is the same as the
direction of displacement of body.

17.  Uniform velocity:
A body has uniform
velocity if it travels in a specified direction
in a straight line and moves over equal
distances in equal intervals of time, no
matter how small how these time intervals
may be.
The velocity of a body can be changed
in two ways:
(i) By changing the speed of the body, and
(ii) By keeping the speed constant but by
changing the direction.

18.  Speed and Velocity are not always
equal in magnitude.
 The magnitude of speed and velocity of
a moving body is equal only if the body
moves in a single straight line. If,
however a body does not move in a
single straight line, then the speed &
velocity of the body is not equal.
 The average speed of a moving can
never be zero, but the average velocity
of a moving body can be zero.

19.  Acceleration:
Acceleration of a body is
defined as the rate of change in velocity
with time.
Formula for Acceleration is:
Acceleration = Final velocity – Initial velocity
Time taken
a = v-u
t

20. Where, a = acceleration of the body
v = final velocity of the body
u = initial velocity of the body
and t = time taken for the
change in velocity
 The SI unit of acceleration is “meter
per second square.”
 Acceleration is a vector quantity
because it has magnitude as well as
direction.

21.  Uniform Acceleration:
A body has a
uniform acceleration if the velocity
changes at a uniform rate.
 Example of Uniform Acceleration:
i. The motion of a freely falling body.
ii. The motion of a bicycle going down
the slope of a road when the rider is
not pedaling and wind is negligible.
iii. The motion of a ball rolling down an
inclined plane.

22.  The velocity-time graph of a body
having uniformly accelerated motion is
a straight line.
 Non-Uniform Acceleration:
A body has
a non-uniform acceleration if its
velocity changes at a non-uniform rate.
 Retardation:
It is the negative of
acceleration.

23. GRAPHOF RETARDATION

24. GRAPH OF NON-UNIFORM
ACCELERATION

25.  If the velocity of a body increases the
acceleration is positive and if the
velocity decreases the acceleration is
negative.
Formula for Retardation is:
Retardation = Final velocity – Initial velocity
Time taken
 SI unit of retardation is meter per
second square.
 Retardation is actually acceleration
with negative sign.

26.  Average Velocity:
If the object is
changing at uniform rate, then average
velocity is given by the arithmetic mean
of initial velocity & final velocity for a
given period of time.
Formula for average velocity:
Average velocity = Initial velocity+ Final velocity
2

27.  Derivation of Formula for Equation
of Motion:
 Equation 1- V = u+at

28.  Consider a velocity time graph for a
body moving under uniform
acceleration ‘a’
Initial velocity u ≠ o
In the v-t graph
OA = DC = u (initial velocity)
EO = BC = v (final velocity)
AD = OC = t (time taken)
BD = BC - DC
= v - u

29. The slope of v-t graph gives the
acceleration of the object.
acceleration ‘a’
a = BD = (v-u)
AD t
or v-u = at
or v = u+at

30.  Equation 2- S= ut + ½ at^2

31. v-t graph
Let the body travels distance ‘s’ in time ‘t’
under uniform acceleration ‘a’.
Distance travelled (s) = area enclosed under
the velocity time graph.
S = area of triangle ABD
+ area of rectangle OADC
= ½  AD BD AO OC
= AD = OC = t
BD = EA =(v-u)
AO = DC = u

32. OC = AD = t
= ½  t  (v-u)  ut
= ut  ½ (v-u) t : Equation 1
We know that
v u  at
 v  u  at : Equation 2
Putting the value of
v  u  at in Equation 1
We get,
s  ut + ½ (at) t
s  ut  ½ at²

33. Equation 3- v²  u²  2as

34. v-t graph
Let the body travels distance ‘s’ in time ‘t’
under uniform acceleration ‘a’.
Distance travelled (s) = area enclosed under
the velocity time graph.

35. In the trapezium OABC
Area  ½ (sum of parallel side) height
 ½  OC (OA  CB)
Distance travelled (s)
s  ½  t (u  v)
We know that v  u  at
t  v  u
a
s  ½  v  u v  u
a

36.  Circular Motion:
When a body moves in
a circle, it is called circular motion.
 When a body moves along a circular
path, then its direction of motion keeps
changing continuously.
 Uniform Circular Motion:
When a body
moves in circular path with uniform
speed, its motion is called uniform
circular motion.

37. s  v²  u²
2a
v²  u²  2as
or v²  u²  2as

38.  The force is needed to produce circular
motion.
 Centripetal Force:
The force which is
needed to make an object travel in a
circular path is called centripetal force.
 Example of Uniform Circular Motion:
i. Artificial satellite move in a circular
motion around the earth.
ii. The moon moves around the earth.
iii. The earth moves around the sun.

39. iv. A athlete moving on a circular path
with a constant speed.
v. The tip of a second’s hand of a watch.
 To Calculate the Speed of a Body in
Uniform Circular Motion:
v  2  22  r
7  t

40. SUMITTED TO
MR KHANKRIAL SIR
SUMITTED FROM
BISHMAY
IX ‘C’