FAQs

MCQs

1. Which law explains the relationship between mass and gravitational force?

A) Newton’s Third Law
B) Newton’s Law of Universal Gravitation
C) Kepler’s Laws
D) Law of Conservation of Momentum

2. What is the value of the gravitational constant (G) in Newton’s Law of Universal Gravitation?

A) \( 6.674 \times 10^{-11} \, \text{N m}^2 \, \text{kg}^{-2} \)
B) \( 9.8 \, \text{m/s}^2 \)
C) \( 9.81 \, \text{m/s}^2 \)
D) \( 10 \, \text{m/s}^2 \)

3. What is the effect of increasing the distance between two objects on the gravitational force?

A) The force increases
B) The force decreases
C) The force remains the same
D) The force becomes zero

4. What is the effect of the Earth’s gravity on a satellite in orbit?

A) The satellite is pulled toward the Earth
B) The satellite is pulled away from the Earth
C) The satellite remains unaffected
D) The satellite moves at a constant speed

5. What happens to the weight of an object if the acceleration due to gravity decreases?

A) The weight increases
B) The weight decreases
C) The weight remains the same
D) The weight becomes zero

GS Mains Questions and Model Answers

Q1: Explain the role of gravitational force in shaping planetary orbits. How does it influence the motion of celestial bodies?

Answer: Gravitational force is the fundamental force responsible for the orbital motion of planets and other celestial bodies. It acts as the centripetal force that keeps planets in orbit around stars, such as the Sun. This force is attractive and is proportional to the masses of the objects involved, with stronger masses exerting a stronger pull. The gravitational force also influences the trajectories of comets, asteroids, and moons, ensuring that they follow predictable paths. Newton’s Law of Universal Gravitation and Kepler’s laws describe this relationship, where the closer an object is to the central body, the stronger the gravitational pull it experiences, which results in a faster orbit.

Q2: How does gravitational force affect daily life on Earth? Discuss its practical implications.

Answer: Gravitational force is fundamental to daily life on Earth as it is responsible for keeping everything grounded. It determines the weight of objects, which impacts everything from how we carry loads to the functioning of machinery. Gravitational force also causes tides in the oceans, driven by the Moon’s gravitational pull. In transportation, gravitational considerations are essential for building structures like bridges, tunnels, and dams, which must account for the Earth’s gravitational pull. Additionally, gravitational force impacts sports, especially those involving jumping or throwing, where the force of gravity determines the height or distance achieved.

Q3: Evaluate the significance of understanding gravitational force for space exploration. How does this knowledge aid in the launch and trajectory planning of spacecraft?

Answer: Understanding gravitational force is crucial for space exploration, as it influences the launch, trajectory, and orbital mechanics of spacecraft. Gravitational calculations help scientists determine the amount of thrust needed to launch a spacecraft and to break free from Earth's gravity. The force also dictates the path of spacecraft once they are in orbit, which is essential for interplanetary travel. Gravitational assist maneuvers, used to increase the speed of spacecraft by utilizing the gravitational field of planets, rely on a deep understanding of gravitational forces. Accurate gravitational modeling ensures that missions are efficient and precise, preventing costly errors.

Previous Year Questions on Gravitational Force

1. UPSC CSE Prelims 2020:

Question: Which of the following statements regarding gravitational force is correct?

A) Gravitational force is a vector quantity
B) Gravitational force is independent of the masses of the two objects
C) Gravitational force is always attractive
D) Gravitational force only acts between objects on Earth

Answer: (C)

Explanation: Gravitational force is always attractive, acting between masses and pulling them toward each other. This is a fundamental property of gravity, as described by Newton’s law of gravitation.

2. UPSC CSE Mains 2019 (GS Paper 1):

Question: “Discuss how Newton’s Law of Universal Gravitation helped in understanding the motion of planets. How does it apply to the motion of celestial bodies in the solar system?”

Answer: Newton’s Law of Universal Gravitation established that every mass in the universe attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between them. This law provided a framework to understand planetary orbits and celestial motion. It explained Kepler’s laws of planetary motion and demonstrated that planets orbit the Sun due to the Sun’s gravitational pull. This law also applies to the motion of moons around planets, asteroids, and the behavior of comets in the solar system.