Tiêu đề 08. Gravitation Easy.pdf ✅

1. The tidal waves in the sea are primarily due to (a) The gravitational effect of the moon on the earth (b) The gravitational effect of the sun on the earth (c) The gravitational effect of Venus on the earth (d) The atmospheric effect of the earth itself 2. If there were a smaller gravitational effect, which of the following forces do you think would alter in some respect (a) Viscous forces (b) Archimedes uplift (c) Electrostatic force (d) None of the above 3. A satellite of the earth is revolving in a circular orbit with a uniform speed v. If the gravitational force suddenly disappears, the satellite will (a) Continue to move with velocity v along the original orbit (b) Move with a velocity v, tangentially to the original orbit (c) Fall down with increasing velocity (d) Ultimately come to rest somewhere on the original orbit 4. The atmosphere is held to the earth by (a) Winds (b) Gravity (c) Clouds (d) None of the above 5. The weight of a body at the centre of the earth is (a) Zero (b) Infinite (c) Same as on the surface of earth (d) None of the above 6. If the distance between two masses is doubled, the gravitational attraction between them (a) Is doubled (b) Becomes four times (c) Is reduced to half (d) Is reduced to a quarter 7. Which of the following is the evidence to show that there must be a force acting on earth and directed towards the sun (a) Deviation of the falling bodies towards east (b) Revolution of the earth round the sun (c) Phenomenon of day and night (d) Apparent motion of sun round the earth 8. The gravitational force between two stones of mass 1 kg each separated by a distance of 1 metre in vacuum is (a) Zero (b) 6.675 × 10 −5newton (c) 6.675 × 10 −11newton (d) 6.675 × 10 −8newton 9. Two particles of equal mass go round a circle of radius R under the action of their mutual gravitational attraction. The speed of each particle is (a) R Gm v 1 2 1 = (b) R Gm v 2 = (c) R Gm v 2 1 = (d) R Gm v 4 = 10. The earth (mass = 6 × 10 24kg)) revolves round the sun with angular velocity 2 × 10 −7 rad/s in a circular orbit of radius 1.5 × 10 8km. The force exerted by the sun on the earth in newtons, is (a) 18 × 10 25 (b) Zero (c) 27 × 10 39 (d) 36 × 10 21 11. Gravitational mass is proportional to gravitational (a) Field (b) Force (c) Intensity (d) All of these 12. The gravitational force between two point masses m1 and m2 at separation r is given by 2 1 2 r m m F = k The constant k (a) Depends on system of units only (b) Depends on medium between masses only (c) Depends on both (a) and (b) (d) Is independent of both (a) and (b) 13. The distance of the centres of moon and earth is D. The mass of earth is 81 times the mass of the moon. At what distance from the centre of the earth, the gravitational force will be zero (a) 2 D (b) 3 2D (c) 3 4D (d) 10 9D 14. Who among the following gave first the experimental value of G (a) Cavendish (b) Copernicus (c) Brook Teylor (d) None of these 15. The mass of the moon is 7.34 × 10 22kg and the radius is 1.74 × 10 6m. The value of gravitation force will be (a) 1.45 N/kg (b) 1.55 N/kg (c) 1.75 N/kg (d) 1.62 N/kg 16. The centripetal force acting on a satellite orbiting round the earth and the gravitational force of earth acting on the satellite both equal F. The net force on the satellite is
(a) Zero (b) F (c) F 2 (d) 2 F 17. Reason of weightlessness in a satellite is (a) Zero gravity (b) Centre of mass (c) Zero reaction force by satellite surface (d) None 18. Mass M is divided into two parts xM and . For a given separation, the value of x for which the gravitational attraction between the two pieces becomes maximum is (a) (b) (c) 1 (d) 2 19. The force of gravitation is (a) Repulsive (b) Electrostatic (c) Conservative (d) Non-conservative 20. The gravitational force Fg between two objects does not depend on (a) Sum of the masses (b)Product of the masses (c) Gravitational constant (d)Distance between the masses 21. Weightlessness experienced while orbiting the earth in space- ship, is the result of (a) Inertia (b) Acceleration (c) Zero gravity (d) Free fall towards earth 22. If the change in the value of ‘g’ at a height h above the surface of the earth is the same as at a depth x below it, then (both x and h being much smaller than the radius of the earth) (a) x = h (b) x = 2h (c) 2 h x = (d) 2 x = h 23. The time period of a simple pendulum on a freely moving artificial satellite is (a) Zero (b) 2 sec (c) 3 sec (d) Infinite 24. Two planets have the same average density but their radii are R1 and R2 . If acceleration due to gravity on these planets be 1 g and 2 g respectively, then (a) 2 1 2 1 R R g g = (b) 1 2 2 1 R R g g = (c) 2 2 2 1 2 1 R R g g = (d) 3 2 3 1 2 1 R R g g = 25. An iron ball and a wooden ball of the same radius are released from a height ‘h’ in vacuum. The time taken by both of them to reach the ground is (a) Unequal (b) Exactly equal (c) Roughly equal (d) Zero 26. The correct answer to above question is based on (a) Acceleration due to gravity in vacuum is same irrespective of size and mass of the body (b) Acceleration due to gravity in vacuum depends on the mass of the body (c) There is no acceleration due to gravity in vacuum (d) In vacuum there is resistance offered to the motion of the body and this resistance depends on the mass of the body 27. When a body is taken from the equator to the poles, its weight (a) Remains constant (b) Increases (c) Decreases (d) Increases at N-pole and decreases at S-pole 28. A body of mass m is taken to the bottom of a deep mine. Then (a) Its mass increases (b) Its mass decreases (c) Its weight increases (d) Its weight decreases 29. A body weighs 700 gm wt on the surface of the earth. How much will it weigh on the surface of a planet whose mass is 7 1 and radius is half that of the earth (a) 200 gm wt (b) 400 gm wt (c) 50 gm wt (d) 300 gm wt 30. In order to find time, the astronaut orbiting in an earth satellite should use (a) A pendulum clock (b) A watch having main spring to keep it going (c) Either a pendulum clock or a watch (d) Neither a pendulum clock nor a watch 31. A spherical planet far out in space has a mass M0 and diameter D0 . A particle of mass m falling freely near the surface of this planet will experience an acceleration due to gravity which is equal to (a) GM0/D0 2 (b) 4mGM0/D0 2 (c) 4GM0/D0 2 (d) GmM0/D0 2 32. If the earth stops rotating, the value of ‘g’ at the equator will (a) Increase (b) Remain same (c) Decrease (d) None of the above 33. The mass and diameter of a planet have twice the value of the corresponding parameters of earth. Acceleration due to gravity on the surface of the planet is (a) 2 9.8 m / sec (b) 2 4.9m / sec (1 − x) M 2 1 5 3
(c) 2 980m / sec (d) 2 19.6m / sec 34. As we go from the equator to the poles, the value of g (a) Remains the same (b) Decreases (c) Increases (d) Decreases up to a latitude of 45° 35. Force of gravity is least at (a) The equator (b) The poles (c) A point in between equator and any pole (d)None of these 36. The radius of the earth is 6400 km and 2 g = 10m / sec . In order that a body of 5 kg weighs zero at the equator, the angular speed of the earth is (a) 1/80 radian/sec (b) 1/400 radian/sec (c) 1/800 radian/sec (d) 1/1600 radian/sec 37. The value of ‘g’ at a particular point is 9.8m/s 2 . Suppose the earth suddenly shrinks uniformly to half its present size without losing any mass. The value of ‘g’ at the same point (assuming that the distance of the point from the centre of earth does not shrink) will now be (a) 4.9m/ sec2 (b) 3.1m/ sec2 (c) 9.8m/ sec2 (d) 19.6m/ sec2 38. If R is the radius of the earth and g the acceleration due to gravity on the earth's surface, the mean density of the earth is (a) 4G / 3gR (b) 3R / 4gG (c) 3g / 4RG (d) RG / 12G 39. The weight of an object in the coal mine, sea level, at the top of the mountain are 1 2 W , W and W3 respectively, then (a) W1  W2  W3 (b) W1 = W2 = W3 (c) W1  W2  W3 (d) W1  W2  W3 40. The radii of two planets are respectively R1 and R2 and their densities are respectively 1 and 2 . The ratio of the accelerations due to gravity at their surfaces is (a) 2 2 2 2 1 1 1 2 : : R R g g   = (b) 1 2 1 2 1 2 g : g = R R :   (c) 1 2 1 2 2 1 g : g = R  : R  (d) 1 2 1 1 2 2 g : g = R  : R  41. The mass of the earth is 81 times that of the moon and the radius of the earth is 3.5 times that of the moon. The ratio of the acceleration due to gravity at the surface of the moon to that at the surface of the earth is (a) 0.15 (b) 0.04 (c) 1 (d) 6 42. Spot the wrong statement : The acceleration due to gravity ‘g’ decreases if (a) We go down from the surface of the earth towards its centre (b) We go up from the surface of the earth (c) We go from the equator towards the poles on the surface of the earth (d) The rotational velocity of the earth is increased 43. Which of the following statements is true (a) g is less at the earth's surface than at a height above it or a depth below it (b) g is same at all places on the surface of the earth (c) g has its maximum value at the equator (d) g is greater at the poles than at the equator 44. A spring balance is graduated on sea level. If a body is weighed with this balance at consecutively increasing heights from earth's surface, the weight indicated by the balance (a) Will go on increasing continuously (b) Will go on decreasing continuously (c) Will remain same (d) Will first increase and then decrease 45. The value of g on the earth's surface is 980cm/ sec2 . Its value at a height of 64 km from the earth's surface is (a) 960.40cm/ sec2 (b) 984.90cm/ sec2 (c) 982.45cm/ sec2 (d) 977.55cm/ sec2 (Radius of the earth R = 6400 kilometers) 46. Choose the correct statement from the following: Weightlessness of an astronaut moving in a satellite is a situation of (a) Zero g (b) No gravity (c) Zero mass (d) Free fall 47. If the earth rotates faster than its present speed, the weight of an object will (a) Increase at the equator but remain unchanged at the poles (b) Decrease at the equator but remain unchanged at the poles (c) Remain unchanged at the equator but decrease at the poles (d) Remain unchanged at the equator but increase at the poles 48. If the earth suddenly shrinks (without changing mass) to half of its present radius, the acceleration due to gravity will be (a) g/2 (b) 4g (c) g/4 (d) 2g 49. The moon's radius is 1/4 that of the earth and its mass is 1/80 times that of the earth. If g represents the acceleration due to gravity on the surface of the earth, that on the surface of the moon is (a) g/4 (b) g/5