Class 11 Physics Chapter 7 Gravitation – Extra Questions with Answers

Every satellite orbiting Earth, including a geostationary one with its fixed 24-hour period, obeys the same gravitational law that governs falling objects. These Class 11 Physics Chapter 7 questions work through orbital velocity, the variation of g with height, and Kepler’s laws.

Last Updated: September 23, 2026

Very Short Answer Questions (1 mark)

Q1. What is the value of the universal gravitational constant G?
Ans: 6.67×10⁻¹¹ Nm²/kg².

Q2. Write the formula for orbital velocity of a satellite.
Ans: v_o=√(GM/r).

Q3. What is a geostationary satellite?
Ans: A satellite orbiting Earth with a period of 24 hours, appearing stationary relative to a point on Earth’s surface.

Q4. How does the value of g vary with height above Earth’s surface?
Ans: g decreases with height above Earth’s surface.

Q5. State Kepler’s second law.
Ans: The radius vector from the Sun to a planet sweeps out equal areas in equal intervals of time.

Short Answer Questions (2–3 marks)

Q6. Two masses of 4 kg and 6 kg are 2 m apart. Find the gravitational force between them (G=6.67×10⁻¹¹ Nm²/kg²).
Ans: F=Gm1m2/r²=6.67×10⁻¹¹(4)(6)/4=4×10⁻¹⁰ N (approx).

Q7. If Earth’s mass is 6×10²⁴ kg and radius 6.4×10⁶ m, find the acceleration due to gravity at the surface.
Ans: g=GM/R²=6.67×10⁻¹¹(6×10²⁴)/(6.4×10⁶)² ≈ 9.8 m/s².

Q8. Find the escape velocity from Earth given g=9.8 m/s² and R=6.4×10⁶ m.
Ans: v_e=√(2gR)=√(2×9.8×6.4×10⁶)≈11.2 km/s.

Higher-Order Thinking / Application Questions

Q9. A planet orbits the Sun at a distance 4 times that of Earth. Using Kepler’s third law, find the ratio of its orbital period to Earth’s orbital period, and explain the reasoning.
Ans: By Kepler’s third law, T²∝r³. So T_planet/T_Earth = (r_planet/r_Earth)^3/2 = 4^3/2 = 8. The planet’s orbital period is 8 times that of Earth. This follows because Kepler’s third law establishes a fixed proportionality between the cube of the orbital radius and the square of the period for all bodies orbiting the same central mass (the Sun).

Q10. Explain why astronauts in an orbiting spacecraft experience weightlessness even though Earth’s gravity is still acting on them, relating this to the concept of free fall.
Ans: Astronauts in orbit are in a state of continuous free fall toward Earth, but because the spacecraft has enough horizontal (tangential) velocity, it keeps ‘missing’ the Earth as it falls, resulting in a circular orbit. Since both the astronaut and the spacecraft are accelerating toward Earth at the same rate (due to gravity alone, with no other supporting force acting on the astronaut relative to the spacecraft), there is no normal force between the astronaut and the spacecraft floor, which is what we perceive as weight. Hence, despite gravity still acting on them, astronauts experience apparent weightlessness because they are in a state of free fall along with their spacecraft.

Quick visual: a worked diagram from the full Solutions page, for reference.

Frequently Asked Questions

How would you find the escape velocity from a planet with mass and radius similar to Earth?
Using v = root(2GM over R), the escape velocity for Earth-like values comes out to about 11.2 km per second.

If a satellite orbits at a height where gravitational acceleration is one-fourth of that on the surface, how does its orbital radius compare?
Since g varies as 1 over r squared, one-fourth the surface value means the orbital radius is twice the surface radius.

Written by Satish

NCERTBooks.org is an independent educational resource run by a small team focused on making official NCERT textbooks easy to find, read, and download for students, parents, and teachers across India. We are not affiliated with NCERT or the Ministry of Education -- we organise publicly available NCERT content by class and subject, verify links against official sources, and build tools (like our in-browser reader) that make studying more convenient. Every guide we publish is written and reviewed by our team based on the actual NCERT curriculum and syllabus.