Physics-DPP-1-9.Gravitation

PHYSICS Topic: GRAVITATION Date: 1. When a body is lifted from surface of earth to height equal to radius of earth, then the change in its PE is : (a) mg R (b) 2 mgR (c) 1 mgR 2 (d) 4 mgR 2. Satellite is revolving around earth. If it’s radius of orbit is increased to 4 times of the radius of geostationary satellite, what will become its time period : (a) 8 days (b) 4 days (c) 2 days (d) 16 days 3. The escape velocity from earth is ve. A body is projected with velocity 2ve. With what constant velocity will it move in the inter planetary space : (a) ve (b) 2 ve (c) 3 ve (d) 5 ve 4. The angular speed of earth in rad/s, so that the object on equator may appear weightless, is : (radius of earth = 6400 km). (a) 1.23 × 10–3 (b) 6.20 × 10–3 (c) 1.56 (d) 1.23 × 10–5 5. With what velocity should a particle be projected so that its height becomes equal to radius of earth ? 1 (a) æçGM ö÷2 (b) (b) 1 æç8GMö÷2 1 (c) æç2GM ö÷2 (d) (d) 1 æç4GM ö÷2 R ø÷ èç R ø÷ èç R ø÷ èç R ø÷ 6. A particle is projected vertically upwards from the surface of earth (radius R) with a kinetic energy equal to half of the minimum value needed for it to escape. The height to which it rises above the surface of earth is : (a) R (b) 2 R (c) 3R (d) 4 R 7. In order to find time, the astronauts orbiting in an earth satellite should use (a) a pendulam clock (b) a watch having main spring to keep it going (c) either a watch ro a pendulam clock (d) neither a watch nor a pendulam clock. 8. Suppose the gravitational attraction varies inversely as the distance from the earth. The orbital velocity of a satellite in such a case varies as nth power of distance, where n is equal to : (a) – 1 (b) zero (c) + 1 (d) + 2 9. Consider a planet moving in an elliptical orbit around the sun. The work done on the planet by the gravitational force of the sun : (a) is zero in every small part of the orbit (b) is zero in some parts of the orbit (c) is zero in one complete revolution (d) is zero in no part of the motion 10. If gravitational attraction between two points masses be given by F = G m1m2 . Then the period of a satellite in a circular orbit will rn be proportional to : (a) n- 1 r 2 (b) n+ 1 r 2 n (c) r 2 (d) independent of n PHYSICS Topic: GRAVITATION Date: 1. (c) 2. (a) Answer Key 3. (c) 4. (a) 5. (a) 6. (a) 7. (b) 8. (b) 9. (b,c) 10. (b)

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