Chapter 8: Motion - PowerPoint Presentation, Science, class IX - Class 9 PDF Download

 Page 1


CHAPTER - 8
MOTION
CLASS :- IX 
MADE BY :- NAMAN
SCHOOL :- K.V . 
Page 2


CHAPTER - 8
MOTION
CLASS :- IX 
MADE BY :- NAMAN
SCHOOL :- K.V . 
1) Describing motion :-
i) Motion :- is the change in position of a body with  time.
Motion can be described in terms of the distance moved or the 
displacement.
ii) Distance moved :- is the actual length of the path travelled by a 
body.
iii) Displacement :- is the length of the shortest path travelled by a 
body from its initial position to its final position. 
Eg :- If a body starts moving in a straight line from origin O and 
moves through C and B and reaches A and then moves back and 
reaches C through B, then
Distance travelled  = 60 + 35 = 95 km
Displacement        = 25 km
O                                     C               B                                         A       
0     5     10   15     20     25    30     35    40     45     50     55     60    km
Page 3


CHAPTER - 8
MOTION
CLASS :- IX 
MADE BY :- NAMAN
SCHOOL :- K.V . 
1) Describing motion :-
i) Motion :- is the change in position of a body with  time.
Motion can be described in terms of the distance moved or the 
displacement.
ii) Distance moved :- is the actual length of the path travelled by a 
body.
iii) Displacement :- is the length of the shortest path travelled by a 
body from its initial position to its final position. 
Eg :- If a body starts moving in a straight line from origin O and 
moves through C and B and reaches A and then moves back and 
reaches C through B, then
Distance travelled  = 60 + 35 = 95 km
Displacement        = 25 km
O                                     C               B                                         A       
0     5     10   15     20     25    30     35    40     45     50     55     60    km
2) Uniform motion and Non uniform motion :-
i) Uniform motion :- If a body travels equal distances in equal intervals of           
time, it is said to be in uniform motion.
ii) Non uniform motion :- If a body travels unequal distances in equal 
intervals of time, it is said to be in non uniform motion.
iii) Speed :- of a body is the distance travelled by the body in unit time.
Distance
Speed =  
Time 
If a body travels a distance  s  in time  t  then its speed  v  is
s
v  =  
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.
iv) Average speed :- is the ratio of the total distance travelled to the total time 
taken.
Total distance travelled 
Average speed  =   
Total time taken  
Page 4


CHAPTER - 8
MOTION
CLASS :- IX 
MADE BY :- NAMAN
SCHOOL :- K.V . 
1) Describing motion :-
i) Motion :- is the change in position of a body with  time.
Motion can be described in terms of the distance moved or the 
displacement.
ii) Distance moved :- is the actual length of the path travelled by a 
body.
iii) Displacement :- is the length of the shortest path travelled by a 
body from its initial position to its final position. 
Eg :- If a body starts moving in a straight line from origin O and 
moves through C and B and reaches A and then moves back and 
reaches C through B, then
Distance travelled  = 60 + 35 = 95 km
Displacement        = 25 km
O                                     C               B                                         A       
0     5     10   15     20     25    30     35    40     45     50     55     60    km
2) Uniform motion and Non uniform motion :-
i) Uniform motion :- If a body travels equal distances in equal intervals of           
time, it is said to be in uniform motion.
ii) Non uniform motion :- If a body travels unequal distances in equal 
intervals of time, it is said to be in non uniform motion.
iii) Speed :- of a body is the distance travelled by the body in unit time.
Distance
Speed =  
Time 
If a body travels a distance  s  in time  t  then its speed  v  is
s
v  =  
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.
iv) Average speed :- is the ratio of the total distance travelled to the total time 
taken.
Total distance travelled 
Average speed  =   
Total time taken  
3) Speed with direction :-
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.
i) Velocity :- of a body is the displacement of the body per unit time.                               
Displacement
Velocity  =    
Time taken 
Since velocity has both magnitude and direction, it is a vector quantity.
ii) Average velocity :- is the ratio of the total displacement to the total 
time taken.  
Total displacement
Average velocity  =   
Total time taken
Average velocity is also the mean of the initial velocity u and final velocity v. 
Initial velocity  +  Final velocity                    u  +  v
Average velocity  =                                                              v
av 
=  
2                                                 2  
Speed and velocity have the same units  m/s  or  ms 
-1
Page 5


CHAPTER - 8
MOTION
CLASS :- IX 
MADE BY :- NAMAN
SCHOOL :- K.V . 
1) Describing motion :-
i) Motion :- is the change in position of a body with  time.
Motion can be described in terms of the distance moved or the 
displacement.
ii) Distance moved :- is the actual length of the path travelled by a 
body.
iii) Displacement :- is the length of the shortest path travelled by a 
body from its initial position to its final position. 
Eg :- If a body starts moving in a straight line from origin O and 
moves through C and B and reaches A and then moves back and 
reaches C through B, then
Distance travelled  = 60 + 35 = 95 km
Displacement        = 25 km
O                                     C               B                                         A       
0     5     10   15     20     25    30     35    40     45     50     55     60    km
2) Uniform motion and Non uniform motion :-
i) Uniform motion :- If a body travels equal distances in equal intervals of           
time, it is said to be in uniform motion.
ii) Non uniform motion :- If a body travels unequal distances in equal 
intervals of time, it is said to be in non uniform motion.
iii) Speed :- of a body is the distance travelled by the body in unit time.
Distance
Speed =  
Time 
If a body travels a distance  s  in time  t  then its speed  v  is
s
v  =  
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.
iv) Average speed :- is the ratio of the total distance travelled to the total time 
taken.
Total distance travelled 
Average speed  =   
Total time taken  
3) Speed with direction :-
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.
i) Velocity :- of a body is the displacement of the body per unit time.                               
Displacement
Velocity  =    
Time taken 
Since velocity has both magnitude and direction, it is a vector quantity.
ii) Average velocity :- is the ratio of the total displacement to the total 
time taken.  
Total displacement
Average velocity  =   
Total time taken
Average velocity is also the mean of the initial velocity u and final velocity v. 
Initial velocity  +  Final velocity                    u  +  v
Average velocity  =                                                              v
av 
=  
2                                                 2  
Speed and velocity have the same units  m/s  or  ms 
-1
4) Rate of change of velocity :-
During uniform motion of a body in a straight line the velocity remains 
constant with time. In this case the change in velocity at any time interval is 
zero ( no change in velocity). 
During non uniform motion the velocity changes with time. In this case the 
change in velocity at any time interval is not zero. It may be  positive (+ ve) or 
negative (- ve).
The quantity which specifies changes in velocity is acceleration.
Acceleration :- is the change in velocity of a body per unit time.( or the rate 
of change of velocity.)
Change in velocity
Acceleration  =  
Time
If the velocity of a body changes from initial value u to final value v in time t, 
then acceleration a is
v  - u
a  = 
t
The SI unit of acceleration is ms 
- 2 
Uniform acceleration :- If the change in velocity is equal in equal intervals 
of time it is uniform acceleration.
Non uniform acceleration :- If the change in velocity is unequal in equal 
intervals of time it is non uniform acceleration.