Motion for class 9th

This PPT is based on Physics on Chapter Motion. In this you will find every thing of that chapter with great images. in this PPT their are many animation and images .
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1. Made BY :- Sanchit Class 9 th - C

2. Describing Motion Motion :- Motion is the change in position of a body with time. Motion can be described in terms of the (i) distance moved or the (ii)displacement (i)Distance moved is the actual length of the path travelled by a body. (ii)Displacement is the length of the shortest path travelled by a body from initial position to it’s final position.

3. Example of the motion T he average speed of bullet train is 320km/hrs A car is in motion. Motion of the Ball Downward.

4. 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. Uniform motion and Non uniform motion

5. Example A movement of a asteroid and the bouncing of ball is the example of non uniform motion. The movement of clock’s hand and movement of pendulum is the example of uniform motion

6. 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 meter per second m / s or ms -1 . Since speed has only magnitude it is a scalar quantity.

7. Example The red car is at the speed of 30m/s And, The gray car is at the speed of 40m/s

8. Average speed Average speed :- is the ratio of the total distance travelled to the total time taken.

9. Example Problems Q. A car travels 85km from point A to B , then 45km from point B to C . The total time took was 1.3 hrs. What was the average speed of the Car? Solution of the problem Total distance=Distance covered i)A to B + ii)B to C 85km + 45km= 130km Total Time = 1.3 hrs Average speed = Total Distance Covered/Total time => 130/1.3 km/hrs => 100km/hrs

10. The quantity which specifies both the direction of motion and speed is 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.

11. Example Speed with Direction is known as Velocity

12. Average Velocity Average velocity :- is the ratio of the total displacement to the total time taken. Average velocity =Total Displacement/Total Time. Average velocity is also the mean of the initial velocity u and final velocity v. Average velocity= (initial velocity + finial velocity)/2 or (u+v)/2 Speed and velocity have the same units m/s or ms -1

13. Example Problem Q. If a car changes its speed from 10m/s to 20m/s in just 5 sec. What is the average velocity of the car? Sol. u = 10m/s time taken v = 20m/s = 5sec Average velocity = (u + v)/2 (20m/s + 10m/s)/2 30m/s/2 15m/s

14. The quantity which specifies changes in velocity is acceleration. Acceleration :- is the rate of change of velocity. Acceleration = (Final velocity – initial velocity) / 2 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) /2 The SI unit of acceleration is ms - 2

15. Example Four different ways to accelerate a car.

16. Distance –Time Graph Motion can be represented on the distance time graph. In the 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. This is because in uniform speed a body travels equal distances in equal intervals of time.

17. Example Uniform Motion

18. Derivation of three formula of motion Let a body is moving with initial velocity ‘u’ with uniform acceleration ‘a’ it’s velocity become ‘v’ in time ‘t’ sec. In the meantime it covers the distance ‘s’ The term would be in Acceleration -> m/s 2 Initial and final velocity -> m/s Time -> sec Distance -> m

19. 1 st Equation of motion Acceleration = (v – u)/t a = (v - u)/t at = v – u u + at = v 1 st equation of motion

20. 2 nd Equation of motion Average velocity = (v + u)/2 Distance Travelled = Av. Velocity + time s = (v + u)/2 x t Put v = u + at s = (u + at + u)/2 x t s = (2u+at)/2 x t s = (2ut + at 2 ) /2 s = ut + ½ at 2 2 nd Equation of motion

21. 3 rd Equation of motion We know that v = u + at v – u = at (v - u)/a = t Put t = (v – u)/a in eq. s = ut + ½ at 2 s = u{(v – u)/a} + ½a {(v-u)/2} 2 s = (uv - u 2 )/a + ½a{(v 2 + u 2 -2uv)/a 2 } s = (uv - u 2 )/a + ½(v 2 + u 2 -2uv)/a s = (uv - u 2 )/a + (v 2 + u 2 -2uv)/2a s = (2uv - 2u 2 + v 2 + u 2 -2uv)/2a s = (v 2 - u 2 )/2a 2as = v 2 - u 2 3 rd Equation of motion

22. Circular motion 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 2 л r. If a body takes time t to go once around the circular path, then the velocity v is given by v = 2 л r/2

23. Example