**Short Questions**

1. A body is moving in a horizontal circle under the action of centripetal force show that work done on it is zero?

2. A loaf of bread is lying on a rotating plate.A crow takes away the leaf of bread and the plates rotation increases.Why?

3. A motorcyclist move in a death well but does not fall.Why?

4. A pilot experience negative weight while flying a jet plane.What is the state of motion of the jet plane?

5. An elevator is moving down when suddenly the chains of elevator break.Two different bodies appear to be having same weight.What is their weight and why?

6. Can a body move along a circle without centripetal force?

7. Centripetal and centrifugal reaction are equal in magnitude but opposite in direction.Do they balance each other?

8. Define angular displacement.

9. Define Angular momentum. Angular velocity

10. Define centripetal force?

11. Define Moment of Inertia. Write its formula.

12. Define weightlessness and Gravity free system.

13. Describe four phenomena in which we have angular momentum?

14. Describe the uses of Geo-stationary satellites?

15. Differentiate between apparent weight and real weight:

16. Distinguish between centripetal force and centrifugal force?

17. Explain artificial gravity?

18. Explain how many minimum of geo- stationary satellites are required for global coverage of TV transmission?

19. Explain the difference between tangential velocity and angular velocity. Write the formula which relates them.

20. Explain weightlessness in satellites.

21. Explain what is meant by centripetal force and why it must be furnished to an object if the object is to follow a circular path?

22. Explain why an object orbiting the Earth is said to be freely falling.(b)Use your explanation to point out why object appear weightless under certain circumstances?

23. Explain why earth’s satellite despite of being freely falling object does not reach the earth.

24. Give an example of motion of body when the direction of acceleration is different from the direction of its velocity?

25. How is artificial gravity created?

26. How the rotation of Earth will be affected it this density becomes uniform?

27. How would acceleration due to gravity vary while going on the surface of earth from equator to North pole or South pole?

28. How would the weight of a body vary as it is taken to the center of the earth?

29. If a body of mass ‘m’ is suspended from the ceiling of an elevator with a string having tension ‘T’such that T=mg.If the elevator is descending with an acceleration ‘a’ what would be the value of ‘T’?

30. If the weight of a body on the earth is defined as w=mg where m =mass of the body and g=acceleration due to gravity.The same body is than taken to the Moon.What would be the weight and mass of the body on the surface of the Moon?

31. Is any work done by centripetal force?

32. Is it possible to distinguish between a raw egg and a hard boiled one by spinning each on a table?

33. It is harder for a car to turn round a corner at high speed than at low speed.Why?

34. Object orbiting around the earth in said to be a freely falling body. Why?

35. Satellites orbiting at different altitudes have different time periods?

36. Show that orbital angular momentum Lᵒ= mvr ?

37. State the direction of the following vectors in simple situations;angular momentum and angular velocity?

38. State the law of conversation of angular momentum.

39. State the right hand rule to find the direction of angular displacement.

40. The apparent weight of a freely falling body is zero.why?

41. The cylinders A and B are of the same mass but the radius of A is greater than that of B.Which one will require more force to come into rotation?Why?

42. Two spheres of copper and lead have same mass.It is found that the lead sphere can be rotated more easily.Explain why?

43. Under what condition a spaceship in the space is said to be weightless?

44. What are Artificial Satellites?

45. What are geostationary orbit and geostationary satellites?

46. What are Geostationary satellites?

47. What are satellites and how they move around the earth?

48. What do you mean by orbital velocity and artificial gravity?

49. What do you understand by apparent weight of a body in a moving elevator?

50. What does Intelsat stand for?Also describe the microwave frequencies for its operation.?

51. What is angular momentum?

52. What is artificial satellite?

53. What is escape velocity?

54. What is meant by centripetal force? Write down its formula.

55. What is meant by moment of inertia? Explain its significance.

56. What is moment of inertia? Give its unit?

57. What is rotational kinetic energy? Give its practical use?

58. What is the difference between spin angular momentum(Ls) and orbital angular momentum (Lᵒ)?

59. What will be the advantage if angle is measured in radians rather than in degrees?

60. When mud flies off the tyre of a moving bicycle, in what direction does it fly? Explain.

61. When mud flies off the Tyre of moving bicycle in what direction does it fly?

62. Why are the banked tracks needed for turns?

63. Why break drum of vehicles are of large diameters?

64. Why does a diver change his body position before and after diving in the water?

65. Why does a diver change his body positions before diving in the pool?

66. Why does a person present in an orbiting satellite feel weight lessness?

67. Why the microwaves are used in satellite communication?

68. Why you wear seat belts?

69. Write some applications of law of conservation of angular momentum ?

70. Write the relation between degree and radian.How many radians are there in 2 degrees?

71. You have disc hoop of same mass and size which of two has moment of inertia and why.

**Long Questions**

1. What is Geo- Stationary Satellite?

2. On what factors, moment of inertia depends?

3. Show that S=rθ

4. Write down applications of communication satellites.

5. Give an example to illustrate law of conservation of angular momentum.

6. Why Einstein‟s theory of gravity is better than Newton‟s?

7. Why the motion of projection of a point revolving in a circle with a variable angular velocity is not Simple harmonic motion.

8. Define and explain centripetal force.

9. Define rotational K.E. and find rotational K.E. of the disc. and hoop.

10. Define artificial satellites. Find the expression for minimum velocity and period.

11. What are real and apparent weight? Find the apparent weight in different cases for an object suspended by a string and spring balance in a lift.

12. What are geostationary orbits and geostationary satellites? Find the orbital radius of geostationary satellites

13. What is orbital velocity and derive an expression for orbital velocity?

14. What is artificial gravity? Derive expression for frequency of spaceship required to provide the artificial gravity?

15. A tiny laser beam is directed from the Earth to the Moon. If the beam is to have a diameter of 2.50 m at the Moon, how small must divergence angle be for the beam? The distance of Moon from the Earth is 3.8 x 10⁸ m.

16. A gramophone record turntable accelerate from rest to an angular velocity of 45.0 rev per min in 1.60 s. What is its average angular acceleration?

17. A body of moment of inertia I = 0.80 kg m² about a fixed axis, rotates with constant angular velocity of 100 rad/s. Calculate its angular momentum L and the torque to sustain this motion.

18. Consider the rotating cylinder shown in book figure 5.26. Suppose that m= 5 kg, F = 0.60 N and r = 0.20 m. Calculate (a) the torque acting on the cylinder, (b) the angular acceleration of the cylinder. (Moment of inertia of cylinder = 1/2mr²

19. Calculate the angular momentum of a star of mass 2 x 10³⁰ kg and radius 7 x 10⁵ Km. If it makes one complete rotation about its axis once in 20 days, what is its kinetic energy?

20. A 1000 kg car traveling with a speed of 144 kmh⁻¹ rounds a curve of radius 100m. Find the necessary centripetal force.

21. What is the least speed at which an aero plane can execute a vertical loop of 1 km radius so that there will be no tendency for the pilot to fall down at the highest point?

22. The moon orbits the Earth so that the same side always faces the Earth. Determine the ratio of its spin angular momentum (about its own axis) and its orbital angular momentum. (In this case, treat the Moon as a particle orbiting the Earth). Distance between the Earth and the Moon is 3.85 x 10⁸m. Radius of the Moon is 1.74 x 10⁶m.

23. The earth rotates on its axis once a day. Suppose by some process the Earth contracts so that its radius is only half as large as at present. How fast will it be rotating then? (for sphere I = 2/5 Mr²).

24. What should be the orbiting speed to launch a satellite in a circular orbit 900km above the surface of the Earth? (Take mass of the Earth as 6 x 10²⁴ kg and its radius as 6400km).