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## Sunday, March 13, 2011

### CBSE Important Questions For Science Class IX(physics)

Q.1. what is persistence of hearing? (1)
Q.2. what does the slope of speed-time graph indicate? (2)
Q.3. what is one Newton? (1)
Q.4. why will a sheet of paper fall lower than one that is crumpled into a ball? (2)
Q.5. A stone is dropped from the edge of a roof.
1. How long does it take to fall 4.9m?

2. How fast does it move at the end of that fall?

3. How does it move at the end of 7.9m?

4. What is its acceleration after 1 second and after 2 second? (4)
Q.6. A boy and a girl do the same work in 5 min and 10 min respectively. Which of these has more power and why? (1)
Q.7. (a) What name has been given to the force with which two objects lying a part attract each other?
(b) What happens to the gravitational force between two objects when the distance between them is:
(i) doubled
(ii) half (2)
Q.8. (a) what is the condition for a force to do work on a body?
(b) A boy throws a rubber ball vertically upwards. What type of work, positive or negative is done.
(i) By force applied by boy?
(ii) By the gravitational force of earth? (3)
Q.9. name the characteristics of sound which depends on:
(i) Amplitude
(ii) waveform
Q.10. give one use of ultrasound in industry and one in hospitals? (1)
Q.11. A sonar station picks up a return signal after 3seconds. How far away is object? (speed of sound in water=1440m/s) (1)
Q.12. Name that part of ear which vibrates when outside sound fall on it? (1)
Q. 13. When the passenger m oving in a bus , the road side trees appear to b e moving ---------------------------------- (a) Back ward (b)For ward
Q. 14. In uniform motion the object covers ------------ (a) equel distance (b) un equal distance
Q. 15. Where objects cover un equal distances in equal interval of time then the motion is called ---------------- (a) uniform motion (b) non uniform motion
Q. 16. The average speed = =A car accelerate = (a) Total time taken /total distance traveled (b) Total distance traveled/total time taken
Q. 17. v = (a) t/s (b) s/t
Q. 18. An object travels 16m in 4sec and another 16 m in 2 sec. what is the average speed of the object----------- (a) 5.33 ms-1 (b) 5. 34 ms-1
Q. 19. If we specify , its direction of motion along with its speed , the quantity that specifies with the aspects is called------------- (a) velocity (b) motion
Q. 20. Automobiles are fitted with a device that show the distance traveled . such a device is known ---------- (a) odometer (b) Speedo meter
Q. 21. The velocity of an object can be -------------- (a) non uniform or variable (b) uniform or variable
Q. 22. Average velocity = (a) initial velocity + final velocity/ 2 (b) initial velocity + final velocity/1
Q. 23. Average velocity = (a) placement/ total time taken (b) Displacement/ total time taken
Q. 24. Acceleration = (a) change in velocity/ time taken (b) change in motion / time
Q. 25. S = (a) ut + 1/2at2 (b) ut + 1 at2
Q. 26. A car accelerate uniformly from 18 km h-1 to 36 km h-1 in 5 sec . calculate the acceleration------------- (a) 1ms-2(b) 1 ms-3
Q. 27. A train starting from rest attaind a velocity of 72 km h-1 in 5 minutes . Assuming that the acceleration is uniform. Find the distance traveled by the train for attaing this velocity --------------------------------- (a) 2km (b) 5 km
Q . 28. Define SI unit of force.(1)
Q . 29. A body is moving with a uniform speed of 15 m/s on a circular track. Why is its motion called acceleration motion.(1)
Q . 30. What is the distance travelled and displacement of a body as its moves from A to B via C.(2)

Q . 31. A motor boat starting from rest on a lake accelerates in a straight line at a constant rate of 2m/s2 for 4 seconds. How far does the boat travels during this time.(2)
Q . 32. Name the force which keeps various planets in their orbits. Write down the formula for the force which exists between two bodies of mass m1 and m2 separated by a distance R from each other.(2)
Q . 33. State Newton’s second law of motion. A ball is thrown on a smooth surface with a force and it stops after some time. Is it supporting First law of motion. Give reasons for your answers.(2)
Q . 34. Velocity-time graph of a body is given above. Answer the following questions (3)
1. Which part of the graph shows uniform acceleration.
2. Which part of the graph shows uniform retardation.
3. Calculate the total distance travelled by the body.
4. Which part of the graph shows zero acceleration.(3)
Q . 35.
1. Derive the first equation of motion v=u + at graphically.
2. Write the equation describing the principle of conservation of momentum.
3. Why does the Gun recoil when a bullet is fired from it. (5)