CBSE Class 11 Physics Gravitation Objective Questions

1. The gravitational field due to a mass distribution is E = K/x³ in the x-direction, where K is a constant. Taking the gravitational potential to be zero at infinity, its value at a distance x is
(a) K/x (b) K/2x (c) K/x² (d) K/2x²

2. A planet of mass m moves around the sun of mass M in an elliptical orbit. The maximum and minimum distance of the planet from the sun are r1 and r2 respectively. The time-period of the planet is proportional to
(a) r1^3/2 (b) r2^3/2 (c) (r1 + r2)^3/2 (d) (r1 – r2)^3/2

3. A particle hanging from a spring stretches it by 1 cm at earth’s surface. Radius of earth is 6400 km. At a place 800 km above the earth’s surface, the same particle will stretch the spring by
(a) 1 cm (b) 8 cm (c) 0.1 cm (d) 0.79 cm

4. A satellite is to revolve around the earth in a circle of radius 8000 km. The speed at which this satellite be projected into orbit will be
(a) 8 km/s (b) 7.08 km/sec (c) 16 km/s (d) 3 km/sec.

5. If the distance between the earth and the sun were half its present value, the number of days in a year would have been
(a) 64.5 (b) 129 (c) 182.5 (d) 730

6. An artificial satellite moving in a circular orbit around the earth has a total kinetic and potential energy equal to E0. Its potential energy is
(a) – E₀ (b) 1.5 E₀ (c) 2 E₀ (d) E₀

7. A planet has twice the density of earth but the acceleration due to gravity on its surface is exactly the same as on the surface of earth. Its radius in terms of radius of earth R will be
(a) R/4 (b) R/2 (c) R/3 (d) R/8

8. Two identical copper spheres each of radius R are placed in contact with each other. If the gravitational attraction between them is F, then
(a) F ∝ R² (b) F ∝ R⁴ (c) F ∝ 1/R² (d) F ∝ 1/R⁴

9. Suppose ge be the acceleration due to gravity at the equator and gp be that at the poles. Assuming earth to be a sphere of radius Re rotating about its own axis with angular speed ω, then gp – ge is given by
(a) ω²/Re (b) Reω² (c) ω²Re² (d) ω²/Re²

10. An infinite number of masses, each of 1 kg, are placed on the positive x-axis at 1 m, 2 m, 4 m, 8 m,.......from the origin. The magnitude of the gravitational field at the origin due to this distribution of masses is
(a) 2G (b) 4G/3  (c) 3G/4 (d) ∞

11. A satellite is orbiting around the earth. By what percentage should we increase its velocity so as to enable it to escape away from earth ?
(a) 41.4% (b) 50% (c) 82.8% (d) 100%

12. A planet is revolving around the sun in elliptical orbit. Its closest distance from the sun is r and the farthest distance is R. If the orbital velocity of the planet closest to the sun be v, then what is the velocity at the farthest point ?
(a) v r/R  (b) v R/r  (c) v( r/R)^1/2 (d) v( R/r)^1/2

13. A body of mass m rises to a height h = R/5 from the earth’s surface where R is earth’s radius. If g is acceleration due to gravity at the earth’s surface, the increase in potential energy is
(a) m g h (b) (4/5) m g h (c) (5/6) m g h (d) (6/7) m g h

14. Two particles of mass m and M are initially at rest and infinitely separated from each other. Due to mutual interaction they approach each other. Their relative velocity of approach at a distance of separation d between them is

(a) 2 G( d/M+m)  (b) √[ 2G(M +m)/d ]  (c)  √[ 2G(M +m)/d ]   (d) √(2Gd/M+m)

15. The energy needed to lift a 2 kg mass vertically upwards through 2 m distance on a planet whose size is the same and mass 4 times as that of the earth is
(a) 160 J (b) 80 J (c) 40 J (d) 20 J

16. The mean radius of the earth’s orbit around the sun is 1.5 × 10¹¹ m and that of the orbit of mercury is 6 × 10¹⁰ m. The mercury will revolve around the sun in nearly
(a) √2/5 years (b) 2/5 years (c) (2/5)² years (d) (2/5)^3/2 years

17. If a planet has a mass twice that of the earth and its radius is three times that of the earth, then a 1 kg mass on its surface would weigh about
(a) 1.1 N (b) 2.2 N (c) 3.3 N (d) 4.4 N