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DPS MEGACITY, KOLKATA Practice Worksheet CLASS IX PHYSICS 1. Why is rachet essential for screw gauge? 2. Define least count of an instrument. 3. The least count of a screw gauge is 0.02 mm. If the 47th division on circular scale coincides with the line of graduation of main scale, find the circular scale reading. 4. With the help of proper labelled diagram, explain how negative zero error of vernier constant is determined. 5. Calculate the length of second s pendulum on the surface of the moon, where acceleration due to gravity is 1/6th the acceleration due to gravity on earth. 6. What is backlash error? How can it be avoided? 7. Find the relation between the following: i) parsec and lightyear. ii) nanometer and angstrom. 8. Calculate the frequency of oscillations of a simple pendulum of length 0.60m. 9. Find the number of times the heart of a human beings beats in 10 years. Assume that the heart beats once in 0.8 s. 10. Explain how can you obtain the value of acceleration due to gravity from simple pendulum experiment. 11. A simple pendulum is taken to the poles and experiment is being performed to measure time period. Will the pendulum swing faster or slower? Justify your answer. 12. Draw the graph showing the variation of T2 with l. How will you use this graph to determine the value of g (acceleration due to gravity)? 13. The mass of an atom of Nitrogen is 14.0 u. Express it in kg. 14.When is the magnitude of displacement equal to the distance? 15. Give an example of motion of a body moving with constant speed, but variable velocity. Draw the diagram to represent such a motion. 16. A body falls freely from a certain height. Show graphically the relation between the distance fallen and time. 17. What can you say about the motion of the object from the speed time graphs given below: 18. 19. The graph show the journey of a cyclist: 20. Write an expression for distance S covered in time t by a body which was initially at rest and starts moving with constant acceleration a. 21. A body with an initial velocity of 0.09 m/s accelerates uniformly at the rate of 9 cms-2 over a distance of 200 m. Calculate: a. the acceleration in m/s2 b. the final velocity in m/s 22. A body moving with a constant acceleration travels the 3m and 8m respectively in 1s and 2s. Calculate: i) initial velocity. ii) acceleration of body. 23. Derive the second equation of motion from the velocity-time graph. 24. A bullet of mass 10g moving with a velocity of 400 m/s get embedded in a freely suspended wooden block of mass 900g. What is the velocity acquired by the block? 25. A body of mass of 2kg is at rest. What should be the magnitude of force which will make the body move with a speed of 30 m/s at the end of 1s? 26. The tip of second s hand of a clock takes 60 seconds to move once on the circular dial of the clock. If the radius of the dial of the clock be 10.5 cm, calculate the speed of the tip of the second s hand of the clock. 27. More the mass, more difficult it is to move the body from rest . Explain the statement with explain. 28. Two objects A and B have masses m1 and m2 respectively (m1 > m2). If the momentum of the bodies is same, which will have a greater velocity? 29. Explain how, a karate player can break a pile of tiles with a single blow of his hand. 30. What is the change in momentum of a car weighing 1500 kg when its speed increases from 36 km/h to 72 km/s uniformly? 31. Show that the acceleration due to gravity does not depend on the mass of the body. 32. Why would an aircraft be unable to fly on moon? 33. For how long should a force of 100 N act on a body of 20 kg so that it acquires a velocity of 100 m/s? 34. If action is always equal to reaction, explain why a cart pulled by a horse can be moved. 35. A force of 5 N gives a mass m1 an acceleration of 8 m/s2 and a mass m2 an acceleration of 24 m/s2. What acceleration would it give if both the masses are tied together? 36. A ball is thrown vertically upwards from the top of a tower with an initial velocity of 19.6 ms-1 . The ball reaches the ground after 5 s. Calculate: i) the height of the tower, ii) velocity of ball on reaching the ground. g=9.8 m/s2 37. The gravitational force of attraction between two objects is x. Keeping the masses of the objects unchanged, if the distance between the objects is halved, then what will be the magnitude of gravitational force between them? 38. Why are the letters in front of AMBULANCE written in reverse order? 39. An object is kept at 60 cm in front of a plane mirror. If the mirror is now moved 25 cm away from the object, how does the image shift from its previous position? 40. Complete the ray diagram and state three characteristics of the image formed. 41. Calculate the number of images formed in case the two plane mirrors are placed at given angle. 42. In case of a convex mirror, if object is moved away from the mirror, how do the position, size and nature of the image change? 43. State two uses of concave mirror. 44. The erect image formed by a concave mirror is of size double the size of object. How are u and v related? 45. Complete the ray diagrams given below: 46. The focal length of a convex mirror is 40 cm. A point source of light is kept at distance 40 cm from the mirror. Find the distance of image from the mirror. 47. At what distance from a concave mirror of focal length 25 cm should an object be placed so that the size of the image is equal to the size of the object. 48. Why does one use convex mirror instead of a plane mirror as a rear view mirror? 49. When an object of height 1 cm is kept at a distance 4 cm from a concave mirror, its erect image of height 1.5 cm is formed at a distance 6 cm behind the mirror. Find the focal length of mirror. 50. A convex mirror forms an erect image of an object of size one-third the size of object. If radius of curvature of convex mirror is 36 cm. Find the position of the object.
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