Gravitation — 50 High-Yield MCQs (NCERT / NEET)

Covers Newton's law of gravitation, gravitational field & potential, escape velocity, orbital motion, Kepler's laws and related concepts. Correct answer shown after each question.

50 MCQs
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Newton's Law Field & Potential Orbits & Escape Kepler's Laws
1. Newton's universal law of gravitation states that gravitational force between two point masses is proportional to:
A. Product of masses and inverse square of distance
B. Sum of masses and inverse distance
C. Difference of masses and inverse cube of distance
D. Product of masses and distance
Answer: A
2. Value of gravitational constant G is approximately:
A. 6.67 × 10^-11 N·m^2/kg^2
B. 9.8 N/kg
C. 3.14 × 10^8
D. 1.6 × 10^-19
Answer: A
3. Weight of an object on Earth's surface is mg. Which of following gives g?
A. GM/R
B. GM/R^2
C. G/R^2
D. GM^2/R^2
Answer: B
4. Gravitational field (g⃗) at distance r from point mass M is:
A. GM / r^2 (directed away)
B. −GM / r^2 (directed towards)
C. GM^2 / r^2
D. Zero
Answer: B
5. Gravitational potential V at distance r from point mass M (taking zero at infinity) is:
A. +GM/r
B. −GM/r
C. GM/r^2
D. Zero
Answer: B
6. Escape velocity from surface of planet of mass M and radius R is:
A. √(GM/R)
B. √(2GM/R)
C. √(GM/2R)
D. √(G/R)
Answer: B
7. Orbital speed of satellite in circular orbit of radius r around Earth is:
A. √(GM/r)
B. √(2GM/r)
C. (GM/r)^2
D. GM/r
Answer: A
8. For circular orbit, centripetal force is provided by:
A. Tension
B. Gravitational force
C. Friction
D. Electromagnetic force
Answer: B
9. Kepler’s first law states that planetary orbits are:
A. Circles with Sun at centre
B. Ellipses with Sun at one focus
C. Parabolas
D. Hyperbolas
Answer: B
10. Kepler’s second law (equal areas in equal times) implies the conservation of:
A. Energy
B. Linear momentum
C. Angular momentum
D. Mass
Answer: C
11. Kepler’s third law relates orbital period T and semi-major axis a as:
A. T ∝ a
B. T^2 ∝ a^3
C. T^3 ∝ a^2
D. T ∝ a^2
Answer: B
12. Gravitational potential energy of mass m at distance r from Earth (zero at infinity) is:
A. −GMm/r
B. +GMm/r
C. m g r
D. Zero
Answer: A
13. If gravity between Earth and Moon suddenly vanished, Moon would:
A. Fall into Earth
B. Move away in straight line tangent to orbit
C. Remain in orbit
D. Spiral inward
Answer: B
14. Surface gravity on planet of mass M and radius R is proportional to:
A. M/R
B. M/R^2
C. M^2/R^2
D. 1/(MR^2)
Answer: B
15. Escape speed from Earth is about:
A. 7.9 km/s
B. 11.2 km/s
C. 3.5 km/s
D. 20 km/s
Answer: B
16. Work done by gravity when moving a mass around a closed loop is:
A. Positive
B. Negative
C. Zero (conservative force)
D. Depends on path
Answer: C
17. For small height h above Earth's surface (h << R), g at height h is approximately:
A. g(1 + 2h/R)
B. g(1 − 2h/R)
C. g(1 − h/R)
D. g
Answer: B
18. Gravitational field inside a uniform spherical shell (at any internal point) is:
A. GM/r^2
B. Zero
C. Varies linearly with r
D. Infinite
Answer: B
19. Gravitational potential at centre of uniform spherical shell is:
A. −GM/R
B. Zero
C. −3GM/2R
D. +GM/R
Answer: A
20. For two point masses m and m separated by distance r, potential energy is:
A. +G m^2 / r
B. −G m^2 / r
C. Zero
D. G m^2 / r^2
Answer: B
21. Weightlessness experienced by astronauts in orbit is because:
A. No gravity at orbit height
B. Both astronaut and spacecraft are in free fall
C. Zero mass of astronaut
D. Magnetic forces counter gravity
Answer: B
22. If mass of Earth doubled and radius remained same, g on surface would:
A. Double
B. Halve
C. Remain same
D. Become zero
Answer: A
23. A satellite in low Earth orbit has period about 90 minutes. This follows from:
A. Newton's second law
B. Kepler's third law
C. Conservation of energy only
D. Conservation of momentum only
Answer: B
24. Gravitational force inside a uniform solid sphere at distance r from centre varies as:
A. 1/r^2
B. r
C. Constant
D. r^2
Answer: B
25. If two Earth-like planets have same density but different radii, surface gravity scales as:
A. R
B. 1/R
C. R^2
D. 1/R^2
Answer: B
26. Two identical satellites move in circular orbits of radii r and 4r. Ratio of their speeds v1:v2 is:
A. 1:2
B. 2:1
C. 1:4
D. 4:1
Answer: B
27. If potential at infinity is zero, potential at Earth's surface is negative because:
A. Work must be done to bring mass from infinity to surface
B. Earth repels masses
C. Potential defined positive near masses
D. None of above
Answer: A
28. For elliptical orbit with semi-major axis a, total mechanical energy of satellite is:
A. −GMm/2a
B. −GMm/a
C. 0
D. +GMm/2a
Answer: A
29. Tidal forces arise because gravitational field:
A. Is uniform
B. Varies with position (gradient)
C. Is zero
D. Is always attractive
Answer: B
30. If gravitational force between two masses is F at distance r, at distance 2r the force becomes:
A. F/2
B. F/4
C. 2F
D. 4F
Answer: B
31. Gravitational field at surface of Earth is approximately:
A. 9.8 N/kg
B. 1 N/kg
C. 100 N/kg
D. 0.1 N/kg
Answer: A
32. A geostationary satellite orbits above equator with period equal to Earth's rotation. Its altitude is approximately:
A. 36,000 km
B. 1800 km
C. 400 km
D. 10,000 km
Answer: A
33. Work done by gravitational force in bringing a mass from infinity to distance r is:
A. −GMm/r
B. +GMm/r
C. Zero
D. GMm/r^2
Answer: A
34. If two planets are separated by large distance, gravitational force becomes negligible due to:
A. Inverse square law
B. Linear decrease with distance
C. Exponential decay
D. Quantum effects
Answer: A
35. A projectile fired near Earth's surface and neglecting air resistance follows path determined by gravity which is:
A. Central force
B. Uniform field near surface
C. Varies as 1/r^2 across trajectory
D. Zero
Answer: B
36. A particle placed at centre of uniform spherical shell experiences:
A. Attractive force towards centre
B. Net zero gravitational force
C. Repulsive force
D. Infinite force
Answer: B
37. If gravitational potential at point is V, gravitational field magnitude g equals:
A. −∇V (gradient)
B. V^2
C. ∇·V (divergence)
D. Zero
Answer: A
38. A comet in highly elliptical orbit moves fastest at:
A. Aphelion (farthest)
B. Perihelion (nearest)
C. Centre
D. Same speed everywhere
Answer: B
39. If Earth had no rotation, weight of object at equator would be:
A. Slightly more than current
B. Slightly less than current
C. Zero
D. Infinite
Answer: A
40. A satellite's specific orbital energy (energy per unit mass) in circular orbit of radius r is:
A. −GM/(2r)
B. −GM/r
C. +GM/(2r)
D. Zero
Answer: A
41. Two masses m and 4m attract each other with force F at separation r. If both masses doubled and separation doubled, new force is:
A. F
B. 2F
C. F/2
D. 4F
Answer: A
42. The Roche limit is related to:
A. Distance where tidal forces disrupt a satellite
B. Escape velocity
C. Orbital period
D. Gravitational potential
Answer: A
43. If gravitational force provides centripetal force for circular orbit, T^2 ∝ r^3 follows (Kepler). This derivation uses:
A. F = ma and circular motion relations
B. Conservation of angular momentum only
C. Energy conservation only
D. None
Answer: A
44. Gravitational binding energy of a uniform sphere is proportional to:
A. GM^2/R
B. GM/R^2
C. M/R
D. GMR
Answer: A
45. A test mass placed at Lagrange point L1 between Earth and Moon experiences net gravitational and centrifugal forces that:
A. Are balanced
B. Result in strong net attraction to Earth
C. Make it fall to Moon
D. Push it away to infinity
Answer: A
46. If a planet's mass is concentrated at its centre (point mass), gravitational field outside equals that of:
A. Uniform sphere
B. Point mass of same mass at centre
C. Hollow shell
D. Depends on density
Answer: B
47. If a spacecraft moves to higher orbit conserving energy, its speed:
A. Increases
B. Decreases
C. Remains same
D. Oscillates
Answer: B
48. Gravitational field lines around a point mass are:
A. Straight lines pointing away
B. Radial lines pointing towards mass
C. Circular lines
D. Random
Answer: B
49. For a binary star system, reduced mass μ = m1 m2 /(m1 + m2) helps reduce two-body problem to equivalent:
A. Single body with mass μ orbiting fixed centre
B. Two independent bodies
C. No motion
D. Massless test particle
Answer: A
50. Gravitational potential due to uniform sphere at interior point r (r
A. −GM/r
B. −GM(3R^2 − r^2)/(2R^3)
C. Zero
D. −3GM/2R
Answer: B