Important Questions of Gravitation Chapter for CBSE Class 11 Physics

Here are some important questions from Chapter: Gravitation for CBSE Class 11 Physics. These questions cover conceptual, numerical, and derivation-based topics that are frequently asked in exams.

1. Conceptual Questions

1. State and explain Newton’s law of universal gravitation. How does the force of gravity between two objects change when:
   • (a) The distance between them is doubled?
   • (b) The mass of one object is tripled?
2. What is gravitational field intensity? Derive an expression for it.
3. Explain why astronauts feel weightlessness in an orbiting satellite.
4. Why does the value of g decrease with increasing altitude and depth?
5. Distinguish between gravitational mass and inertial mass.
6. Define escape velocity. Derive an expression for escape velocity of a planet.
7. What is geostationary satellite? Mention its characteristics and applications.
8. Why does the Moon not fall onto the Earth even though it is attracted by Earth’s gravity?

2. Derivation-Based Questions

1. Derive an expression for variation of acceleration due to gravity with altitude.
2. Derive an expression for orbital velocity of a satellite revolving around Earth.
3. Derive an expression for gravitational potential energy of a system of masses.
4. Show that Kepler’s second law follows from Newton’s law of gravitation.
5. Derive an expression for the time period of a satellite in terms of orbital radius.
6. Prove that the gravitational potential energy at a height hhh above the Earth’s surface is given by: U=−GMm(R+h)​

3. Numerical Problems

1. The mass of Earth is 5.972×10²⁴ kg and its radius is 6.371×10⁶ m. Calculate:
   • (a) The acceleration due to gravity on its surface.
   • (b) The escape velocity from Earth’s surface.
2. A satellite is orbiting 500 km above the Earth’s surface. If the Earth’s radius is 6400 km, find the orbital velocity of the satellite.
3. The gravitational force between two objects is 10 N when they are 1 m apart. What will be the force if the distance is increased to 4 m?
4. The mass of the Moon is 1/81 of Earth’s mass and its radius is 1/4 of Earth’s radius. Find the acceleration due to gravity on the Moon.
5. If a satellite takes 24 hours to complete one revolution around the Earth, calculate its height above the Earth’s surface.

4. Short Answer & Assertion-Reason Questions

1. Assertion (A): The value of acceleration due to gravity is the same everywhere on the Earth’s surface.
   Reason (R): The Earth is a perfect sphere.
   (a) Both A and R are true, and R is the correct explanation of A.
   (b) Both A and R are true, but R is not the correct explanation of A.
   (c) A is true, but R is false.
   (d) A is false, but R is true.
2. Two satellites of masses m and 2m are orbiting at the same height around Earth. Which has greater orbital speed?
3. Why do polar satellites orbit at lower altitudes compared to geostationary satellites?
4. The weight of an object is 200 N on Earth. What will be its weight on the Moon?
5. A body is dropped from a height of 100 m. How much time will it take to reach the ground? (Ignore air resistance)