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1. Who was the first scientist to propose the universal law of gravitation?
ⓐ. Albert Einstein
ⓑ. Galileo Galilei
ⓒ. Isaac Newton
ⓓ. Johannes Kepler
Correct Answer: Isaac Newton
Explanation: Newton first proposed the Universal Law of Gravitation in 1687. Kepler described planetary motion laws but did not explain the force behind them. Galileo studied falling bodies, and Einstein later extended Newton’s work with General Relativity.
2. According to Newton’s law of gravitation, the force between two masses is:
ⓐ. Inversely proportional to the product of masses
ⓑ. Directly proportional to the square of the distance
ⓒ. Directly proportional to the product of masses
ⓓ. Inversely proportional to the distance
Correct Answer: Directly proportional to the product of masses
Explanation: Gravitational force \(F\) is given by \(F = G \frac{m_1 m_2}{r^2}\). It is directly proportional to the product of the masses and inversely proportional to the square of the distance between them.
3. What is the SI unit of the universal gravitational constant \(G\)?
ⓐ. \(\text{Nm/kg}\)
ⓑ. \(\text{Nm}^2/\text{kg}^2\)
ⓒ. \(\text{m}^2/\text{kg}^2\)
ⓓ. \(\text{kg}^2/\text{Nm}^2\)
Correct Answer: \(\text{Nm}^2/\text{kg}^2\)
Explanation: From Newton’s law, \(F = G \frac{m_1 m_2}{r^2}\). Rearranging for \(G\), we get \(G = \frac{Fr^2}{m_1 m_2}\). Substituting SI units: \(N \cdot m^2 / kg^2\).
4. Which of the following correctly represents Newton’s law of gravitation?
ⓐ. \(F = G \frac{m_1 + m_2}{r}\)
ⓑ. \(F = G \frac{m_1 m_2}{r}\)
ⓒ. \(F = G \frac{m_1 m_2}{r^2}\)
ⓓ. \(F = \frac{m_1 m_2}{Gr^2}\)
Correct Answer: \(F = G \frac{m_1 m_2}{r^2}\)
Explanation: The universal law states that gravitational force is directly proportional to the product of the two masses and inversely proportional to the square of the distance between them.
5. The value of \(G\) was first determined by:
ⓐ. Newton
ⓑ. Cavendish
ⓒ. Kepler
ⓓ. Galileo
Correct Answer: Cavendish
Explanation: In 1798, Henry Cavendish measured the value of \(G\) using a torsion balance experiment. Newton proposed the law but did not measure \(G\).
6. The gravitational force between two bodies will become four times if:
ⓐ. Distance between them is halved
ⓑ. Distance is doubled
ⓒ. Both masses are halved
ⓓ. One mass is doubled and distance is doubled
Correct Answer: Distance between them is halved
Explanation: \(F \propto \frac{1}{r^2}\). If \(r\) becomes \(r/2\), then \(F \propto 1/(r/2)^2 = 4/r^2\). Hence, force becomes 4 times.
7. Which of the following statements about gravitational force is correct?
ⓐ. It is always repulsive
ⓑ. It is stronger than the electrostatic force
ⓒ. It acts along the line joining the two masses
ⓓ. It acts only on Earth
Correct Answer: It acts along the line joining the two masses
Explanation: Gravitational force is always attractive and acts along the line joining the centers of the two bodies. It is much weaker than electrostatic force but has an infinite range.
8. If the mass of one body is doubled, then gravitational force between two bodies becomes:
ⓐ. Half
ⓑ. Double
ⓒ. Four times
ⓓ. Unchanged
Correct Answer: Double
Explanation: Since \(F \propto m_1 m_2\), if one mass is doubled, the product doubles, and hence the force also doubles.
9. What is the dimensional formula of \(G\)?
ⓐ. \([M^{-1} L^3 T^{-2}]\)
ⓑ. \([M L^3 T^{-2}]\)
ⓒ. \([M^{-2} L^2 T^{-2}]\)
ⓓ. \([M^{-1} L^2 T^{-2}]\)
Correct Answer: \([M^{-1} L^3 T^{-2}]\)
Explanation: From \(F = G \frac{m_1 m_2}{r^2}\), we get \(G = \frac{Fr^2}{m^2}\). Substituting dimensional formulas:
\(F = [M L T^{-2}]\), \(r^2 = [L^2]\), \(m^2 = [M^2]\).
So, \(G = [M L T^{-2}] [L^2] / [M^2] = [M^{-1} L^3 T^{-2}]\).
10. Which one of the following is a consequence of the universal law of gravitation?
ⓐ. Tides in oceans
ⓑ. Revolution of planets around the Sun
ⓒ. Motion of satellites around Earth
ⓓ. All of the above
Correct Answer: All of the above
Explanation: The law explains planetary motion, satellite motion, and ocean tides. The gravitational pull of the Moon and Sun causes tides, while the Earth–Sun gravitational force keeps planets in orbit.
11. Who gave the three laws of planetary motion that later helped Newton to formulate the law of gravitation?
ⓐ. Copernicus
ⓑ. Kepler
ⓒ. Galileo
ⓓ. Ptolemy
Correct Answer: Kepler
Explanation: Johannes Kepler proposed three empirical laws of planetary motion in the early 17th century. These laws explained how planets orbit the Sun in ellipses, sweep equal areas in equal times, and relate orbital period to distance. Newton later used these to establish the universal law of gravitation.
12. Which ancient philosopher first suggested that every object has a natural place and tends to move toward it?
ⓐ. Aristotle
ⓑ. Archimedes
ⓒ. Pythagoras
ⓓ. Plato
Correct Answer: Aristotle
Explanation: Aristotle (384–322 BCE) believed that objects have a “natural place” — for example, stones fall to Earth because their natural place is on the ground. This idea dominated for centuries until Galileo and Newton introduced scientific reasoning.
13. Who proposed the heliocentric model of the solar system before Kepler and Newton?
ⓐ. Tycho Brahe
ⓑ. Ptolemy
ⓒ. Copernicus
ⓓ. Galileo
Correct Answer: Copernicus
Explanation: Nicolaus Copernicus proposed the heliocentric model in the 16th century, placing the Sun at the center of the solar system. This challenged the Ptolemaic Earth-centered model and paved the way for Kepler and Newton.
14. Galileo’s experiments on falling bodies showed that:
ⓐ. Heavier objects fall faster than lighter ones
ⓑ. All objects fall at the same rate in vacuum
ⓒ. The Earth attracts only living things
ⓓ. Falling depends on size not mass
Correct Answer: All objects fall at the same rate in vacuum
Explanation: Galileo demonstrated that in the absence of air resistance, objects fall with the same acceleration regardless of mass. This refuted Aristotle’s belief that heavier objects fall faster.
15. Which astronomer’s precise observations of planetary motion allowed Kepler to formulate his laws?
ⓐ. Newton
ⓑ. Tycho Brahe
ⓒ. Copernicus
ⓓ. Halley
Correct Answer: Tycho Brahe
Explanation: Tycho Brahe made accurate naked-eye observations of planetary positions. After his death, Kepler used Brahe’s data to formulate his three laws of planetary motion.
16. The statement “Every object in the Universe attracts every other object with a force” was first mathematically given by:
ⓐ. Newton
ⓑ. Galileo
ⓒ. Kepler
ⓓ. Copernicus
Correct Answer: Newton
Explanation: Newton’s universal law of gravitation (1687) was the first to mathematically describe the gravitational attraction between all objects with mass.
17. Which concept by Galileo was crucial for Newton’s first law of motion?
ⓐ. Natural place of objects
ⓑ. Inertia of rest and motion
ⓒ. Epicycles of planets
ⓓ. Crystal spheres of stars
Correct Answer: Inertia of rest and motion
Explanation: Galileo introduced the concept of inertia, showing that objects continue in motion unless acted upon by external forces. Newton later incorporated this into his First Law of Motion, forming a basis for gravitation studies.
18. Why were Kepler’s laws considered incomplete before Newton?
ⓐ. They ignored circular orbits
ⓑ. They were not based on accurate data
ⓒ. They described motion but not the cause of motion
ⓓ. They applied only to Earth
Correct Answer: They described motion but not the cause of motion
Explanation: Kepler’s laws were descriptive (empirical) — they explained how planets move but did not explain why. Newton later provided the physical explanation using the law of universal gravitation.
19. Who is often credited with “measuring the mass of the Earth” using the gravitational constant?
ⓐ. Newton
ⓑ. Galileo
ⓒ. Cavendish
ⓓ. Kepler
Correct Answer: Cavendish
Explanation: Henry Cavendish (1798) used the torsion balance to measure \(G\), which allowed calculation of the Earth’s mass and density. His work is famously described as “weighing the Earth.”
20. Which statement best describes the transition from ancient to modern ideas of gravitation?
ⓐ. From Earth-centered motion to heliocentric motion to universal laws
ⓑ. From heliocentric to geocentric model of the universe
ⓒ. From Newton to Aristotle to Galileo
ⓓ. From tides to planets to satellites
Correct Answer: From Earth-centered motion to heliocentric motion to universal laws
Explanation: Ancient models (Aristotle/Ptolemy) emphasized a geocentric universe. Copernicus introduced heliocentrism, Kepler described orbital laws, Galileo explained motion with experiments, and Newton unified these with the universal law of gravitation.
21. Which of the following phenomena can be explained by the universal law of gravitation?
ⓐ. Falling of an apple from a tree
ⓑ. Motion of the Moon around Earth
ⓒ. Tides in oceans
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Gravitation explains both terrestrial phenomena (falling of objects, tides) and celestial phenomena (orbital motion of the Moon and planets). Newton’s law unified these under one principle.
22. Why is the study of gravitation important in astronomy?
ⓐ. It helps in understanding atomic structure
ⓑ. It explains the motion of celestial bodies
ⓒ. It describes chemical bonding
ⓓ. It explains sound propagation
Correct Answer: It explains the motion of celestial bodies
Explanation: Gravitation is the force that governs the motion of planets, stars, galaxies, and other astronomical bodies. Without it, stable orbits and structures in the universe would not exist.
23. Which of the following is NOT influenced by gravitation?
ⓐ. Satellites orbiting Earth
ⓑ. Electrons revolving around nucleus
ⓒ. Planets orbiting the Sun
ⓓ. Formation of black holes
Correct Answer: Electrons revolving around nucleus
Explanation: Electrons are bound by electromagnetic force, not gravity. Gravitation affects large-scale structures like planets, satellites, and stars, whereas electromagnetic force dominates at the atomic level.
24. How does gravitation affect tides on Earth?
ⓐ. Tides occur only due to Earth’s rotation
ⓑ. Tides occur due to gravitational pull of the Moon and Sun
ⓒ. Tides occur due to Earth’s magnetic field
ⓓ. Tides occur randomly without cause
Correct Answer: Tides occur due to gravitational pull of the Moon and Sun
Explanation: The Moon’s gravitational pull primarily causes tides, while the Sun’s gravity also contributes. The differential gravitational pull on Earth’s oceans leads to high and low tides.
25. Why is gravitation considered a universal force?
ⓐ. It acts only between celestial bodies
ⓑ. It acts only on Earth
ⓒ. It acts between any two objects with mass in the universe
ⓓ. It acts only on charged particles
Correct Answer: It acts between any two objects with mass in the universe
Explanation: Gravitation has no exceptions; it applies to all objects with mass, irrespective of size or location, hence called a universal force.
26. Why is the study of gravitation essential for launching artificial satellites?
ⓐ. It ensures the satellites generate electricity
ⓑ. It helps in determining orbital velocity and stability
ⓒ. It makes satellites lighter
ⓓ. It prevents atmospheric drag
Correct Answer: It helps in determining orbital velocity and stability
Explanation: Satellites remain in orbit due to the balance between gravitational force and their tangential velocity. Gravitation calculations are critical to ensure stability and correct positioning.
27. Which force is responsible for holding galaxies together?
ⓐ. Electrostatic force
ⓑ. Nuclear force
ⓒ. Gravitational force
ⓓ. Magnetic force
Correct Answer: Gravitational force
Explanation: Gravitation is the only long-range attractive force acting across vast distances. It binds stars into galaxies and galaxies into clusters, shaping the large-scale structure of the universe.
28. What role does gravitation play in the life cycle of stars?
ⓐ. It balances radiation pressure during star formation
ⓑ. It causes nuclear fusion to start
ⓒ. It leads to collapse into white dwarfs, neutron stars, or black holes
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Gravitation pulls gas clouds together to form stars, maintains balance against radiation pressure, and causes collapse after fuel exhaustion, forming white dwarfs, neutron stars, or black holes.
29. Which of the following technologies directly depends on understanding gravitation?
ⓐ. GPS navigation
ⓑ. MRI scanning
ⓒ. Nuclear reactors
ⓓ. Solar cells
Correct Answer: GPS navigation
Explanation: GPS satellites orbit Earth under the influence of gravity. Precise calculations of their orbits and relativistic corrections due to gravitation are essential for accurate positioning.
30. Why is it important to study gravitation in physics education?
ⓐ. It is a minor concept only for theory
ⓑ. It links everyday experiences to cosmic phenomena
ⓒ. It only explains falling bodies
ⓓ. It is outdated due to relativity
Correct Answer: It links everyday experiences to cosmic phenomena
Explanation: Gravitation bridges terrestrial experiences (falling objects, tides) with cosmic scales (planetary motion, galaxy formation). It provides students with a unified understanding of the physical universe.
31. Which law explains why planets revolve around the Sun in elliptical orbits?
ⓐ. Newton’s First Law of Motion
ⓑ. Newton’s Law of Gravitation
ⓒ. Archimedes’ Principle
ⓓ. Pascal’s Law
Correct Answer: Newton’s Law of Gravitation
Explanation: The Sun attracts planets through gravitational force. This central force, inversely proportional to the square of distance, explains why planets move in elliptical orbits as per Kepler’s laws.
32. Why do astronauts in space stations experience weightlessness?
ⓐ. There is no gravity in space
ⓑ. The station is far away from Earth’s gravity
ⓒ. Both astronaut and station are in free fall under gravity
ⓓ. Air resistance cancels weight
Correct Answer: Both astronaut and station are in free fall under gravity
Explanation: Astronauts and the space station fall freely around Earth due to gravity. Since they share the same acceleration, astronauts feel weightless even though gravity is still acting on them.
33. The path of a satellite around Earth is determined by:
ⓐ. Electrostatic force
ⓑ. Nuclear force
ⓒ. Gravitational force
ⓓ. Magnetic force
Correct Answer: Gravitational force
Explanation: A satellite’s motion is governed by Earth’s gravity providing the centripetal force needed to keep it in orbit. Other forces like electromagnetic or nuclear have no role in this large-scale orbital motion.
34. Escape velocity is defined as:
ⓐ. Minimum velocity needed to keep orbiting Earth
ⓑ. Maximum velocity a rocket can attain
ⓒ. Minimum velocity required to overcome Earth’s gravitational pull
ⓓ. Velocity at which weight of a body becomes zero
Correct Answer: Minimum velocity required to overcome Earth’s gravitational pull
Explanation: Escape velocity is the minimum speed required to escape Earth’s gravitational field without further propulsion. For Earth, it is about \(11.2 \, \text{km/s}\).
35. The gravitational pull of the Moon is mainly responsible for:
ⓐ. Solar eclipses
ⓑ. Ocean tides
ⓒ. Day and night cycle
ⓓ. Rotation of Earth
Correct Answer: Ocean tides
Explanation: The Moon’s gravity pulls water on Earth, causing high tides on the near and far sides. This periodic rise and fall of sea level is a direct application of gravitational concepts.
36. Why is gravitation important in understanding planetary atmospheres?
ⓐ. It determines the color of planets
ⓑ. It helps retain atmosphere around planets
ⓒ. It increases atmospheric temperature
ⓓ. It prevents rotation of planets
Correct Answer: It helps retain atmosphere around planets
Explanation: A planet’s gravitational force keeps gases bound to it. Lighter planets with weak gravity (like Mercury) cannot retain thick atmospheres, while Earth’s stronger gravity holds one.
37. Which gravitational concept explains why comets follow elongated paths around the Sun?
ⓐ. Acceleration due to gravity on Earth
ⓑ. Newton’s universal law of gravitation
ⓒ. Hooke’s law
ⓓ. Coulomb’s law
Correct Answer: Newton’s universal law of gravitation
Explanation: Comets follow elliptical or hyperbolic paths due to Sun’s gravity. The variation in distance affects their speed, consistent with Newton’s and Kepler’s laws.
38. How is gravitation used in calculating the mass of celestial bodies like Earth or Moon?
ⓐ. By measuring their density directly
ⓑ. By using orbital motion of satellites around them
ⓒ. By weighing them with a balance
ⓓ. By calculating surface temperature
Correct Answer: By using orbital motion of satellites around them
Explanation: Using \(F = G\frac{Mm}{r^2}\) and centripetal force \(F = \frac{mv^2}{r}\), one can calculate the mass \(M\) of celestial bodies by observing satellite motion parameters.
39. Why does the Sun not collapse under its own gravity?
ⓐ. Because of magnetic fields
ⓑ. Because of nuclear fusion generating outward pressure
ⓒ. Because it rotates very fast
ⓓ. Because it has no gravity
Correct Answer: Because of nuclear fusion generating outward pressure
Explanation: In stars like the Sun, gravity pulls inward while radiation pressure from nuclear fusion pushes outward. This balance, called hydrostatic equilibrium, prevents collapse.
40. What explains the bending of light near massive objects like stars?
ⓐ. Refraction
ⓑ. Gravitational lensing
ⓒ. Diffraction
ⓓ. Polarization
Correct Answer: Gravitational lensing
Explanation: According to Einstein’s general relativity, gravity bends spacetime. Light passing near massive objects like stars or galaxies follows curved paths, producing the phenomenon of gravitational lensing.
41. Kepler’s First Law of planetary motion states that:
ⓐ. Planets revolve in circular orbits around the Sun
ⓑ. Planets revolve in elliptical orbits with the Sun at one focus
ⓒ. Planets revolve in elliptical orbits with the Earth at one focus
ⓓ. Planets revolve in parabolic orbits around the Sun
Correct Answer: Planets revolve in elliptical orbits with the Sun at one focus
Explanation: Kepler’s First Law, the Law of Ellipses, states that planets follow elliptical orbits, not circular, with the Sun occupying one of the two foci of the ellipse.
42. What is the eccentricity of a perfectly circular orbit?
ⓐ. 1
ⓑ. 0
ⓒ. Between 0 and 1
ⓓ. Greater than 1
Correct Answer: 0
Explanation: The eccentricity of an ellipse describes its “ovalness.” For a circle, eccentricity \(e = 0\). Elliptical orbits have \(0 < e < 1\).
43. If the eccentricity of an orbit is close to 1, what does the orbit look like?
ⓐ. Perfect circle
ⓑ. Very elongated ellipse
ⓒ. Parabola
ⓓ. Hyperbola
Correct Answer: Very elongated ellipse
Explanation: Higher eccentricity means more elongated orbits. For planets, eccentricity values are generally small, making them nearly circular, but comets often have high eccentricity.
44. In Kepler’s First Law, what is located at the other focus of the elliptical orbit (not occupied by the Sun)?
ⓐ. Another planet
ⓑ. Nothing
ⓒ. The center of mass of the solar system
ⓓ. A black hole
Correct Answer: Nothing
Explanation: One focus of the ellipse contains the Sun, while the other focus is empty. This is a geometrical property of ellipses.
45. Which of the following planets has the most eccentric orbit in our solar system?
ⓐ. Earth
ⓑ. Venus
ⓒ. Mercury
ⓓ. Mars
Correct Answer: Mercury
Explanation: Mercury has the highest orbital eccentricity (about 0.21) among the major planets, making its orbit more elongated compared to Earth (eccentricity \~0.017).
46. If a planet’s orbit is elliptical, where does it move fastest?
ⓐ. At the aphelion (farthest point from the Sun)
ⓑ. At the perihelion (closest point to the Sun)
ⓒ. At the midpoint of the ellipse
ⓓ. Same speed everywhere
Correct Answer: At the perihelion (closest point to the Sun)
Explanation: A planet moves fastest at perihelion due to stronger gravitational attraction and conservation of angular momentum.
47. What is the semi-major axis of an elliptical orbit?
ⓐ. Half of the longest diameter of the ellipse
ⓑ. Half of the shortest diameter of the ellipse
ⓒ. Distance between the foci
ⓓ. Distance between focus and center
Correct Answer: Half of the longest diameter of the ellipse
Explanation: The semi-major axis is half of the major axis, which is the longest diameter of the ellipse. It is a key parameter in orbital mechanics.
48. Which of the following best describes Earth’s orbit around the Sun?
ⓐ. Highly eccentric ellipse
ⓑ. Nearly circular ellipse
ⓒ. Perfect circle
ⓓ. Parabola
Correct Answer: Nearly circular ellipse
Explanation: Earth’s orbit has an eccentricity of about 0.017, making it very close to circular, but technically still an ellipse as per Kepler’s First Law.
49. The perihelion of Earth occurs in:
ⓐ. January
ⓑ. March
ⓒ. June
ⓓ. September
Correct Answer: January
Explanation: Earth is closest to the Sun (perihelion) in early January and farthest (aphelion) in early July. This is due to the elliptical nature of its orbit.
50. Which of the following celestial bodies typically has the highest orbital eccentricity?
ⓐ. Planets
ⓑ. Comets
ⓒ. Moons
ⓓ. Asteroids
Correct Answer: Comets
Explanation: Comets often have highly eccentric orbits, sometimes approaching 1, making them very elongated ellipses. Planets and moons generally have low eccentricities, closer to circular paths.
51. Kepler’s Second Law of planetary motion states that:
ⓐ. A planet moves with uniform speed in its orbit
ⓑ. A planet sweeps out equal areas in equal intervals of time
ⓒ. A planet always moves faster when farther from the Sun
ⓓ. Planets revolve in circular orbits with the Sun at the center
Correct Answer: A planet sweeps out equal areas in equal intervals of time
Explanation: According to Kepler’s Second Law, the line joining a planet and the Sun sweeps out equal areas in equal times, meaning the planet’s speed varies but the areal velocity remains constant.
52. Which physical principle is most directly related to Kepler’s Second Law?
ⓐ. Conservation of momentum
ⓑ. Conservation of angular momentum
ⓒ. Conservation of energy
ⓓ. Conservation of mass
Correct Answer: Conservation of angular momentum
Explanation: The Second Law arises from the principle of angular momentum conservation. As a planet moves closer to the Sun, velocity increases to maintain constant angular momentum.
53. According to Kepler’s Second Law, a planet moves fastest when it is at:
ⓐ. Aphelion
ⓑ. Perihelion
ⓒ. Midpoint of orbit
ⓓ. Any random point
Correct Answer: Perihelion
Explanation: Near perihelion, the distance from the Sun is minimum, and hence the velocity is maximum to conserve angular momentum, causing the planet to sweep equal areas in equal times.
54. If a planet sweeps out an area of \(2 \times 10^{10} \, \text{km}^2\) in 10 days, then in the next 10 days it will sweep:
ⓐ. A smaller area
ⓑ. A larger area
ⓒ. The same area
ⓓ. Zero area
Correct Answer: The same area
Explanation: By Kepler’s Second Law, equal time intervals correspond to equal areas swept, regardless of where the planet is in its orbit.
55. Which of the following quantities remains constant in Kepler’s Second Law?
ⓐ. Linear velocity
ⓑ. Angular velocity
ⓒ. Areal velocity
ⓓ. Orbital distance
Correct Answer: Areal velocity
Explanation: Areal velocity (area swept per unit time) remains constant. Linear and angular velocities change as the distance from the Sun changes during the orbit.
56. What happens to a planet’s orbital speed as it moves from perihelion to aphelion?
ⓐ. Increases
ⓑ. Decreases
ⓒ. Remains constant
ⓓ. First increases then decreases
Correct Answer: Decreases
Explanation: At perihelion, the planet has maximum speed. As it moves to aphelion, the distance increases and speed decreases, keeping areal velocity constant.
57. Which of the following is a direct observational consequence of Kepler’s Second Law?
ⓐ. Seasons on Earth
ⓑ. Variation in orbital speed of planets
ⓒ. Retrograde motion of planets
ⓓ. Shape of Earth’s orbit
Correct Answer: Variation in orbital speed of planets
Explanation: Kepler’s Second Law explains why a planet’s orbital speed is not uniform: faster at perihelion, slower at aphelion.
58. The area swept per unit time by a planet is mathematically given by:
ⓐ. \(\frac{1}{2} r v\)
ⓑ. \(\frac{1}{2} r^2 \omega\)
ⓒ. Both A and B
ⓓ. None of these
Correct Answer: Both A and B
Explanation: Areal velocity = \(\frac{1}{2} r v \sin\theta\). For perpendicular velocity, it simplifies to \(\frac{1}{2} r v\). In angular form, it is \(\frac{1}{2} r^2 \omega\).
59. The Second Law implies that the force acting on a planet is:
ⓐ. Radial and central
ⓑ. Tangential
ⓒ. Non-existent
ⓓ. Constant in magnitude and direction
Correct Answer: Radial and central
Explanation: For angular momentum conservation, the force must act along the line joining the planet and the Sun, i.e., a central (radial) force.
60. Which of the following planets experiences the greatest variation in orbital speed due to Kepler’s Second Law?
ⓐ. Earth
ⓑ. Venus
ⓒ. Mercury
ⓓ. Neptune
Correct Answer: Mercury
Explanation: Mercury has the highest orbital eccentricity among major planets, so the difference between its perihelion and aphelion speeds is the largest, showing the strongest effect of Kepler’s Second Law.
61. Kepler’s Third Law of planetary motion states that:
ⓐ. The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit
ⓑ. The orbital speed of a planet is constant
ⓒ. The product of mass and acceleration is proportional to gravitational force
ⓓ. Planets revolve in circular orbits around the Sun
Correct Answer: The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit
Explanation: According to Kepler’s Third Law, \(T^2 \propto a^3\), where \(T\) is the orbital period and \(a\) is the semi-major axis of the orbit. This is also called the Law of Harmonies.
62. Which of the following ratios is constant for all planets according to Kepler’s Third Law?
ⓐ. \(\frac{T}{a}\)
ⓑ. \(\frac{T^2}{a^3}\)
ⓒ. \(\frac{T^3}{a^2}\)
ⓓ. \(\frac{T}{a^2}\)
Correct Answer: \(\frac{T^2}{a^3}\)
Explanation: Kepler’s Third Law shows \(\frac{T^2}{a^3}\) is constant for all planets orbiting the same central body. This ratio depends only on the mass of the central object.
63. If the semi-major axis of a planet’s orbit is doubled, its orbital period will:
ⓐ. Remain the same
ⓑ. Become twice
ⓒ. Become four times
ⓓ. Increase by a factor of \(2^{3/2}\)
Correct Answer: Increase by a factor of \(2^{3/2}\)
Explanation: From Kepler’s Third Law, \(T \propto a^{3/2}\). If \(a\) doubles, \(T\) increases by \(2^{3/2} = 2\sqrt{2}\).
64. Which planet takes the longest time to orbit the Sun?
ⓐ. Earth
ⓑ. Mars
ⓒ. Jupiter
ⓓ. Neptune
Correct Answer: Neptune
Explanation: Neptune has the largest semi-major axis among the listed planets, and by Kepler’s Third Law, larger \(a\) means longer orbital period. Neptune takes \~165 years to complete one revolution.
65. Which of the following is a direct application of Kepler’s Third Law?
ⓐ. Calculation of the orbital period of satellites
ⓑ. Determining escape velocity
ⓒ. Calculation of tides
ⓓ. Measurement of gravitational constant \(G\)
Correct Answer: Calculation of the orbital period of satellites
Explanation: The orbital period of artificial satellites around Earth is calculated using \(T^2 \propto r^3\), a direct application of Kepler’s Third Law.
66. For Earth, the ratio \(\frac{T^2}{a^3}\) has what numerical value (approximately)?
ⓐ. 1 year\(^2\)/AU\(^3\)
ⓑ. 365 year\(^2\)/AU\(^3\)
ⓒ. 0
ⓓ. Infinite
Correct Answer: 1 year\(^2\)/AU\(^3\)
Explanation: By definition of an astronomical unit (AU), for Earth \(T = 1 \, \text{year}, a = 1 \, \text{AU}\). Thus, \(\frac{T^2}{a^3} = \frac{1^2}{1^3} = 1\).
67. In Kepler’s Third Law, if \(T\) is measured in years and \(a\) in AU, then the proportionality constant for planets around the Sun is:
ⓐ. 0
ⓑ. 1
ⓒ. 3
ⓓ. 365
Correct Answer: 1
Explanation: For the solar system, when \(T\) is in years and \(a\) in astronomical units, the relation simplifies to \(T^2 = a^3\). The proportionality constant is 1.
68. The Third Law shows that:
ⓐ. Inner planets move slower than outer planets
ⓑ. Outer planets have longer orbital periods than inner planets
ⓒ. All planets have the same orbital period
ⓓ. Orbital period is independent of distance
Correct Answer: Outer planets have longer orbital periods than inner planets
Explanation: Since \(T^2 \propto a^3\), larger distance from the Sun means a longer orbital period. Hence outer planets take much longer to complete an orbit.
69. If a satellite orbits very close to Earth’s surface, which of the following is true about its orbital period?
ⓐ. Around 24 hours
ⓑ. Around 90 minutes
ⓒ. Around 7 days
ⓓ. Infinite
Correct Answer: Around 90 minutes
Explanation: A low Earth orbit satellite has a small orbital radius \(r\), so its period \(T\) is small (about 90 minutes). This follows from \(T^2 \propto r^3\).
70. Kepler’s Third Law was later derived mathematically from which theory?
ⓐ. Special Relativity
ⓑ. Newton’s Law of Gravitation
ⓒ. General Relativity
ⓓ. Quantum Mechanics
Correct Answer: Newton’s Law of Gravitation
Explanation: Newton derived Kepler’s Third Law using his gravitational law and centripetal force. He showed that \(T^2 = \frac{4\pi^2}{GM} a^3\), thus giving a theoretical foundation to Kepler’s empirical law.
71. Kepler’s laws were derived theoretically by Newton using which fundamental law?
ⓐ. Coulomb’s Law
ⓑ. Newton’s Law of Gravitation
ⓒ. Hooke’s Law
ⓓ. Archimedes’ Principle
Correct Answer: Newton’s Law of Gravitation
Explanation: Newton showed that if gravitational force acts as a central inverse-square law, then planetary orbits must satisfy Kepler’s three laws. This provided the theoretical basis for Kepler’s empirical findings.
72. Which mathematical relation combines Newton’s Law of Gravitation with Kepler’s Third Law?
ⓐ. \(T = \frac{2 \pi r}{v}\)
ⓑ. \(T^2 = \frac{4 \pi^2 a^3}{GM}\)
ⓒ. \(F = ma\)
ⓓ. \(T = \frac{a^3}{G}\)
Correct Answer: \(T^2 = \frac{4 \pi^2 a^3}{GM}\)
Explanation: By equating centripetal force \(\frac{mv^2}{r}\) with gravitational force \(\frac{GMm}{r^2}\), Newton derived \(T^2 = \frac{4\pi^2}{GM} a^3\). This links orbital period with semi-major axis and central mass.
73. Kepler’s Second Law can be derived from which principle of physics?
ⓐ. Conservation of linear momentum
ⓑ. Conservation of angular momentum
ⓒ. Conservation of energy
ⓓ. Conservation of mass
Correct Answer: Conservation of angular momentum
Explanation: As the gravitational force is central, torque about the Sun is zero. Hence angular momentum is conserved, implying equal areas are swept in equal time intervals.
74. Which law of Kepler can be applied to calculate the orbital period of a geostationary satellite?
ⓐ. First Law
ⓑ. Second Law
ⓒ. Third Law
ⓓ. None of these
Correct Answer: Third Law
Explanation: The orbital period of a geostationary satellite (24 hours) can be derived using Kepler’s Third Law, relating \(T^2\) to \(r^3\). This ensures the satellite stays fixed relative to Earth’s rotation.
75. If the orbital period of a satellite around Earth is known, which physical quantity can be calculated using Kepler’s Third Law?
ⓐ. Mass of the satellite
ⓑ. Mass of the Earth
ⓒ. Radius of the Earth
ⓓ. Acceleration due to gravity on Moon
Correct Answer: Mass of the Earth
Explanation: By rearranging \(T^2 = \frac{4 \pi^2 r^3}{GM}\), the Earth’s mass \(M\) can be calculated if orbital radius \(r\) and period \(T\) are known.
76. Kepler’s First Law can be theoretically derived using:
ⓐ. Energy conservation and central force concept
ⓑ. Archimedes’ principle
ⓒ. Coulomb’s law of electrostatics
ⓓ. Hooke’s law of elasticity
Correct Answer: Energy conservation and central force concept
Explanation: By solving equations of motion under an inverse-square central force, one finds the trajectory is a conic section (ellipse, parabola, or hyperbola). For bound orbits, the path is an ellipse, proving Kepler’s First Law.
77. Which Kepler’s law is essential for predicting the varying speed of comets in their orbits?
ⓐ. First Law
ⓑ. Second Law
ⓒ. Third Law
ⓓ. Combination of all
Correct Answer: Second Law
Explanation: The Second Law (equal areas in equal time) explains why comets speed up near perihelion and slow down near aphelion, consistent with conservation of angular momentum.
78. Application of Kepler’s Third Law to moons of Jupiter allowed astronomers to:
ⓐ. Prove heliocentric theory
ⓑ. Measure the mass of Jupiter
ⓒ. Calculate Earth’s eccentricity
ⓓ. Disprove Newton’s laws
Correct Answer: Measure the mass of Jupiter
Explanation: By observing orbital periods and distances of Jupiter’s moons, astronomers applied \(T^2 = \frac{4\pi^2}{GM} a^3\) to determine Jupiter’s mass accurately.
79. Derivation of Kepler’s laws from Newton’s gravitation proved that:
ⓐ. Gravitation is only applicable on Earth
ⓑ. The same physical laws apply to celestial and terrestrial bodies
ⓒ. Kepler’s laws were incorrect
ⓓ. Circular orbits are the only possible orbits
Correct Answer: The same physical laws apply to celestial and terrestrial bodies
Explanation: Newton showed that gravitation is universal, applying equally to falling apples and orbiting planets, unifying Earthly and celestial mechanics.
80. The application of Kepler’s laws is crucial in which modern field?
ⓐ. Satellite communication and GPS
ⓑ. Chemical bonding studies
ⓒ. Thermodynamics of gases
ⓓ. Quantum mechanics of atoms
Correct Answer: Satellite communication and GPS
Explanation: Kepler’s Third Law is used to calculate orbital parameters of satellites, ensuring accurate positioning in systems like GPS, telecommunications, and weather forecasting.
81. Which of the following provides the mathematical proof of Kepler’s Third Law?
ⓐ. Equating centripetal force with gravitational force
ⓑ. Applying Newton’s first law
ⓒ. Using Hooke’s law of elasticity
ⓓ. Using Archimedes’ principle
Correct Answer: Equating centripetal force with gravitational force
Explanation: For a planet in orbit, centripetal force \(\frac{mv^2}{r}\) is provided by gravitational force \(\frac{GMm}{r^2}\). Solving with \(v = \frac{2\pi r}{T}\) yields \(T^2 = \frac{4\pi^2}{GM}r^3\), the mathematical basis of Kepler’s Third Law.
82. Kepler’s laws, when derived from Newton’s theory, assume which type of central force?
ⓐ. Linear force
ⓑ. Constant force
ⓒ. Inverse-square law force
ⓓ. Exponential force
Correct Answer: Inverse-square law force
Explanation: Newton showed that an inverse-square central force naturally leads to elliptical orbits, conservation of areal velocity, and \(T^2 \propto a^3\), thus proving Kepler’s laws.
83. The use of Kepler’s Third Law allowed astronomers to first determine the mass of which celestial body other than Earth?
ⓐ. The Sun
ⓑ. The Moon
ⓒ. Mars
ⓓ. Saturn
Correct Answer: The Sun
Explanation: By applying \(T^2 = \frac{4\pi^2}{GM}a^3\) to planetary orbits around the Sun, astronomers were able to calculate the Sun’s mass with high accuracy.
84. Which of Kepler’s laws can be directly applied to prove that gravitational force acts as a central force?
ⓐ. First Law
ⓑ. Second Law
ⓒ. Third Law
ⓓ. Combination of First and Third
Correct Answer: Second Law
Explanation: The fact that planets sweep out equal areas in equal times shows that torque is zero and the force must be directed toward the Sun. This proves that gravity is a central force.
85. Which physical constant can be determined by applying Newton’s form of Kepler’s Third Law to planetary data?
ⓐ. Gravitational constant \(G\)
ⓑ. Mass of the central body
ⓒ. Speed of light \(c\)
ⓓ. Planck’s constant \(h\)
Correct Answer: Mass of the central body
Explanation: The modified Third Law \(T^2 = \frac{4\pi^2}{GM}a^3\) allows calculation of the central mass (Sun, Earth, Jupiter, etc.) if orbital radius and period are known.
86. Which modern technology uses precise applications of Kepler’s laws to function accurately?
ⓐ. Nuclear reactors
ⓑ. GPS navigation systems
ⓒ. Electron microscopes
ⓓ. MRI scanners
Correct Answer: GPS navigation systems
Explanation: GPS satellites orbit Earth in predictable paths derived using Kepler’s Third Law. Accurate timing and positioning rely on understanding and applying these orbital mechanics.
87. Derivation of Kepler’s First Law from Newton’s equations shows that orbital paths can be:
ⓐ. Only circles
ⓑ. Only ellipses
ⓒ. Conic sections (ellipse, parabola, hyperbola)
ⓓ. Random paths
Correct Answer: Conic sections (ellipse, parabola, hyperbola)
Explanation: Solutions of motion under an inverse-square central force yield conic sections. Bound orbits are ellipses, while unbound paths can be parabolic or hyperbolic.
88. How did Newton’s derivation of Kepler’s laws strengthen the concept of universal gravitation?
ⓐ. By showing that gravity applies only to Earth
ⓑ. By uniting terrestrial and celestial mechanics
ⓒ. By proving Kepler’s laws wrong
ⓓ. By explaining only circular motion
Correct Answer: By uniting terrestrial and celestial mechanics
Explanation: Newton showed that the same law of gravitation governs both falling objects on Earth and planetary motion, confirming universality of natural laws.
89. Which application of Kepler’s laws helps in predicting eclipses and transits?
ⓐ. First Law
ⓑ. Second Law
ⓒ. Third Law
ⓓ. Combination of all three laws
Correct Answer: Combination of all three laws
Explanation: Eclipses and transits depend on orbital shape (First Law), speed variations (Second Law), and orbital periods (Third Law). Together, they enable accurate prediction of celestial events.
90. Which of the following was historically one of the first practical applications of Kepler’s laws?
ⓐ. Designing satellites
ⓑ. Navigation and calendar making
ⓒ. Nuclear energy development
ⓓ. Measuring electron charge
Correct Answer: Navigation and calendar making
Explanation: Before satellites, Kepler’s laws were used to predict planetary positions and align calendars with celestial cycles, helping navigation at sea and agricultural planning.
91. Which is the correct statement of the Law of Universal Gravitation?
ⓐ. Every object attracts every other object with a force inversely proportional to the square of the distance between them
ⓑ. Every object attracts every other object with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them
ⓒ. Every object attracts every other object with a constant force regardless of mass and distance
ⓓ. Every object attracts only if one of them is the Earth
Correct Answer: Every object attracts every other object with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them
Explanation: Newton’s Law of Universal Gravitation is mathematically expressed as \(F = G \frac{m_1 m_2}{r^2}\). It is universal because it applies to all masses everywhere.
92. What does the constant \(G\) represent in Newton’s law of gravitation?
ⓐ. Acceleration due to gravity on Earth
ⓑ. A universal proportionality constant
ⓒ. A unitless scaling factor
ⓓ. Mass of the Earth
Correct Answer: A universal proportionality constant
Explanation: \(G\) is the universal gravitational constant with value \(6.67 \times 10^{-11} \, \text{Nm}^2/\text{kg}^2\). It determines the strength of gravitational force between two masses.
93. If the distance between two masses is doubled, the gravitational force becomes:
ⓐ. Double
ⓑ. Half
ⓒ. One-fourth
ⓓ. Four times
Correct Answer: One-fourth
Explanation: Gravitational force is inversely proportional to the square of the distance. If \(r\) becomes \(2r\), then \(F\) becomes \(1/4\) of its original value.
94. Which physical quantity does NOT affect gravitational force between two bodies?
ⓐ. Mass of first body
ⓑ. Mass of second body
ⓒ. Distance between bodies
ⓓ. Their material composition
Correct Answer: Their material composition
Explanation: Gravitational force depends only on mass and distance, not on material or charge. Thus, all objects fall equally in the absence of air resistance.
95. The Law of Universal Gravitation applies to:
ⓐ. Only objects near Earth
ⓑ. Only planets and stars
ⓒ. All objects with mass in the universe
ⓓ. Only objects in vacuum
Correct Answer: All objects with mass in the universe
Explanation: The force of gravitation is universal and acts between all masses, whether large like stars or small like particles of dust.
96. If the mass of both bodies is doubled while keeping the distance constant, the gravitational force becomes:
ⓐ. Unchanged
ⓑ. Double
ⓒ. Four times
ⓓ. Half
Correct Answer: Four times
Explanation: \(F \propto m_1 m_2\). If both masses are doubled, the product increases four times, so the gravitational force becomes four times greater.
97. Which of the following best explains why Newton called his law “universal”?
ⓐ. Because it applied only to planets in the solar system
ⓑ. Because it worked everywhere and for all masses
ⓒ. Because it explained only Earth’s gravity
ⓓ. Because it worked only under vacuum conditions
Correct Answer: Because it worked everywhere and for all masses
Explanation: The universality comes from the fact that Newton’s law applies to any two masses in the universe, regardless of size, distance, or medium.
98. Which of the following equations correctly represents the universal law of gravitation?
ⓐ. \(F = G \frac{m_1 + m_2}{r^2}\)
ⓑ. \(F = G \frac{m_1 m_2}{r^2}\)
ⓒ. \(F = G \frac{m_1 m_2}{r}\)
ⓓ. \(F = G \frac{m_1 + m_2}{r}\)
Correct Answer: \(F = G \frac{m_1 m_2}{r^2}\)
Explanation: The law clearly states that \(F\) is proportional to \(m_1 m_2\) and inversely proportional to \(r^2\). Options A, C, and D are incorrect modifications.
99. The universal law of gravitation was first published in which work by Newton?
ⓐ. Opticks
ⓑ. Principia Mathematica
ⓒ. Laws of Motion
ⓓ. Theory of Relativity
Correct Answer: Principia Mathematica
Explanation: Newton’s *Philosophiæ Naturalis Principia Mathematica* (1687) first described the law of universal gravitation along with the laws of motion.
100. Why is the inverse-square nature of the gravitational law important?
ⓐ. It ensures force decreases rapidly with distance, allowing stable orbits
ⓑ. It prevents objects from colliding in space
ⓒ. It ensures gravity acts only near Earth
ⓓ. It makes force independent of mass
Correct Answer: It ensures force decreases rapidly with distance, allowing stable orbits
Explanation: The \(1/r^2\) dependence makes gravity weaker with distance, enabling celestial bodies to have stable orbits instead of being pulled directly into each other.
Welcome to Class 11 Physics MCQs – Chapter 8: Gravitation (Part 1). This page is a chapter-wise question bank for the NCERT/CBSE Class 11 Physics syllabus—built for quick revision and exam speed. Practice MCQs / objective questions / Physics quiz items with solutions and explanations, ideal for CBSE Boards, JEE Main, NEET, competitive exams, and Board exams.
These MCQs are suitable for international competitive exams—physics concepts are universal.
Navigation & pages: The full chapter has 580 MCQs in 6 parts (100 + 100 + 100 + 100 + 100 + 80). Part 1 contains 100 MCQs split across 10 pages—you’ll see 10 questions per page. Use the page numbers above to view the remaining questions.
What you will learn & practice
- Introduction to Gravitation and celestial mechanics overview
- Kepler’s Laws (orbits, areas, period–radius relation)
- Universal Law of Gravitation and its applications
- Gravitational Constant (G) and measurement basics
- Acceleration due to gravity (g) at Earth’s surface
- Variation of g above the surface and below the surface (height & depth)
- Gravitational potential energy and potential
- Escape speed and energy criteria
- Earth satellites: orbital speed, period, and energy of an orbiting satellite
- Geostationary & polar satellites: features and use-cases
- Weightlessness (free fall, orbit, spaceflight context)
How this practice works
- Click an option to check instantly: green dot = correct, red icon = incorrect. The Correct Answer and brief Explanation then appear.
- Use the 👁️ Eye icon to reveal the answer with explanation without guessing.
- Use the 📝 Notebook icon as a temporary workspace while reading (notes are not saved).
- Use the ⚠️ Alert icon to report a question if you find any mistake—your message reaches us instantly.
- Use the 💬 Message icon to leave a comment or start a discussion for that question.
Real value: Strictly aligned to NCERT/CBSE topics, informed by previous-year paper trends, and written with concise, exam-oriented explanations—perfect for one-mark questions, quick concept checks, and last-minute revision.
The full chapter includes 580 solved multiple-choice questions in 6 parts. This page (Part 1) gives the first 100 MCQs with answers and explanations to build your foundations. Explore more with: Class 11 Physics – Chapter Index, Class 11 – Subject Index, All Classes – MCQ Library.
- 👉 Total MCQs in this chapter: 580 (100 + 100 + 100 + 100 + 100 + 80)
- 👉 This page: first 100 multiple-choice questions with answers & brief explanations (in 10 pages)
- 👉 Best for: Boards • JEE/NEET • chapter-wise test • one-mark revision • quick Physics quiz
- 👉 Next: use the Part buttons and the page numbers above to continue
FAQs on Gravitation ▼
▸ What are Class 11 Physics Chapter 8 Gravitation MCQs?
These are multiple-choice questions from Chapter 8 of NCERT Class 11 Physics – Gravitation. They test your understanding of Newton’s law of gravitation, planetary motion, satellites, escape velocity, and related concepts.
▸ How many MCQs are available in this chapter?
There are a total of 580 MCQs in Gravitation. They are divided into 6 sets – five sets of 100 questions each and one set of 80 questions, all with answers and explanations.
▸ Are these Gravitation MCQs based on NCERT/CBSE syllabus?
Yes, these MCQs strictly follow the NCERT/CBSE Class 11 Physics syllabus and are also useful for state board exams, ensuring complete syllabus coverage.
▸ Are these Gravitation MCQs important for JEE and NEET?
Yes, Gravitation is a high-weightage chapter in competitive exams like JEE and NEET. Concepts such as satellite motion, orbital velocity, and gravitational potential are frequently asked in entrance tests.
▸ Do these MCQs come with answers and explanations?
Yes, each MCQ includes the correct answer and detailed explanation, helping students build strong conceptual clarity and avoid confusion during exams.
▸ What subtopics of Gravitation are covered in these MCQs?
The MCQs cover Newton’s law of gravitation, acceleration due to gravity, variation of gravity with height and depth, orbital motion of satellites, escape velocity, geostationary satellites, and gravitational potential energy.
▸ Are there MCQs on satellites and planetary motion?
Yes, you will find plenty of MCQs on satellites, planetary motion, Kepler’s laws, orbital velocity, and the energy of satellites which are very important for competitive exams.
▸ Who should solve these Gravitation MCQs?
These MCQs are designed for Class 11 students, board exam aspirants, and competitive exam candidates preparing for JEE, NEET, NDA, UPSC, and other entrance tests.
▸ Can I practice these MCQs online for free?
Yes, all Gravitation MCQs are available on GK Aim for free. Students can practice them anytime using mobile, tablet, or desktop.
▸ Are these MCQs good for quick revision before exams?
Yes, practicing these MCQs regularly helps with quick revision, strengthens memory recall, and improves exam performance by enhancing accuracy and speed.
▸ Do these MCQs cover both simple and advanced problems?
Yes, the questions range from basic factual MCQs to advanced application-based problems on gravitation, making them suitable for all levels of learners.
▸ Can teachers and coaching institutes use these MCQs?
Yes, teachers and coaching centers can use these MCQs as ready-made practice sets, quizzes, and assignments for students preparing for school and competitive exams.
▸ Can I download Gravitation MCQs for offline study?
Yes, you can download these Gravitation MCQs in PDF format for offline practice. Please visit our website shop.gkaim.com