Physics-DPP-3-Gravitation

PHYSICS Topic: GRAVITATION Date: 1. A satellite S is moving in an elliptical orbit around the earth. The mass of the satellite is very small compared to the mass of the earth (a) the acceleration of S is always directed towards the centre of the earth. (b) the angular momentum of S about the centre of the earth changes in direction but its magnitude remains constant (c) the total mechanical energy of S varies periodically with time. (d) the linear momentum of S remains constant in the magnitude. 2. If an artificial satellite is moving in a circular orbit around the earth with a speed equal to half the magnitude of the escape velocity from the earth, the height of the satellite above the surface of the earth is : R (a) 2 R (b) 2 R (c) R (d) 4 3. A particle of mass m is projected from the surface of earth with a speed vo (vo < escape velocity). The speed of particle at height h = R (radius of earth) is : (Here, R = 6400 km and g = 9.8 m/s2). (a) (b) (c) (d) none of these 4. A satellite is orbiting very close to planet. Its time period depends only upon : (a) density of the planet (b) mass of the planet (c) radius of the planet (d) mass of the satellite 5. Figure shows the variation of energy with the orbit radius r of a satellite in a circular motion. Mark the correct statement. (a) C shows that total energy, B the kinetic energy and A the potential energy of the satellite. (b) A shows the kinetic energy, B the total energy and C the potential energy of the satellite (c) A and B are the kinetic and potential energies respectively and C the total energy of the satellite. (d) C and A are the kinetic and potential energies respectively and B the total energy of the satellite. 6. The angular momentum (L) of earth revolving round the sun is proportional to rn, where r is the orbital radius of the earth. The value of n is : (assume the orbit to be circular) 1 (a) 2 (b) 1 (c) – 1 2 (d) 2 7. Suppose the gravitational force varies inversely as the nth power of the distance. Then the time period of a planet in circular orbit of radius R around the sun will be proportional to : (a) Rn (b) R(n+ 1)/2 (c) R(n- 1)/ 2 (d) R– n PHYSICS Topic: GRAVITATION Date: 8. Two particles each of mass m are placed at A and C as such AB = BC = L. The gravitational force on the third particle placed at D at a distance L metre of the perpendicular bisector of the line AC, is : (a) Gm2 along BD (b) Gm2 along DB (c) Gm2 L2 along AC (d) none of these 9. A straight rod of length L extends from x = a to x = L + a. The gravitational force exerted by it on a point mass m at x = 0 if the linear density of rod is μ = A + Bx2 , is : éA ù é æç1 1 ö÷ ù é A ù é Aù (a) Gm ê + BLú (b) Gm êAç - ÷+ BLú (c) Gm êBL + ú (d) Gm êBL – ú êëa úû êë èa a + L ø úû ëê a + L úû ëê a úû 10. A gravitational field is present in a region. A point mass is shifted from A to B, from different paths shown in the figure. If W1, W2 and W3 represent work done by gravitational force for respective paths, then : (a) W1 = W2 = W3 (b) W1 > W2 > W3 (c) W1 > W3 > W2 (d) none of these PHYSICS Topic: GRAVITATION Date: 1. (a) 2. (c) Answer Key 3. (c) 4. (a) 5. (c) 6. (a) 7. (b) 8. (b) 9. (b) 10. (a)

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