# Gravitation Notes, Class 11 Physics | SwaVid

Gravitation: NCERT Class 11 Physics notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Written by SwaVid from the textbook.

Canonical: https://www.swavid.com/cbse/class-11/physics/chapter/gravitation

Source: https://www.swavid.com/cbse/class-11/physics/chapter/gravitation

# Gravitation

## Formulas and definitions

## Key ideas

## Common mistakes

## Quick checks

## Keep going

## Questions parents ask

## Class 11 Physics on SwaVid

### Kepler's laws of planetary motion

### Universal law of gravitation

### Acceleration due to gravity

### Gravitational potential energy

### Escape speed and satellites

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SwaVid › CBSE › Class 11 › Physics › Gravitation

Notes written by SwaVid from the NCERT textbook.

Class 11 Physics, Chapter 7. Key ideas, formulas and common mistakes.

CBSE prints 17 marks for Units IV-VI together, not for this chapter alone.

Short answer. This chapter explains Kepler's laws of planetary motion, Newton's universal law of gravitation, and the concept of gravitational potential energy. Students learn how gravity controls the motion of planets, satellites, and objects near or far from the Earth.

Source: NCERT Physics Part I (Reprint 2026-27) , Chapter 7, Gravitation

Planets move in elliptical orbits with the Sun at one focus. The line joining a planet to the Sun sweeps equal areas in equal intervals of time, and the square of the orbital period is proportional to the cube of the semi-major axis.

Every particle attracts every other particle with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them. The force acts along the straight line joining the two particles.

The acceleration produced in a body by Earth's gravitational pull is g = G M / R². It decreases with increasing altitude above the surface and also decreases with depth below the surface.

Gravitational potential energy of two masses separated by distance r is defined relative to zero at infinity. Because the gravitational force is attractive, this potential energy is always negative and equals -G M m / r.

Escape speed is the minimum speed needed for an object to escape Earth's gravitational field completely. Satellites revolve around Earth in stable orbits where the gravitational force provides the necessary centripetal acceleration.

Try each question first. Then tap it to see the answer.

vₑ = √(2 g R)

vₑ = √(2 × 9.8 × 6.4 × 10⁶) = √(125.44 × 10⁶)

vₑ = 11.2 × 10³ m s⁻¹ = 11.2 km s⁻¹

11.2 km s⁻¹

g(d) = g (1 - d / R)

g / 2 = g (1 - d / R)

1 - d / R = 0.5

d = 0.5 × 6400 km = 3200 km

3200 km

F = G m₁ m₂ / r²

F = 6.67 × 10⁻¹¹ × 100 × 100 / (1)²

F = 6.67 × 10⁻⁷ N

6.67 × 10⁻⁷ N

Mechanical Properties of Solids .

Laws of Motion .

Work, Energy and Power .

System of Particles and Rotational Motion .

The 14 chapters of Class 11 Physics .

CBSE does not give marks to one chapter. It prints 17 marks for Units IV-VI together (Work, Energy and Power; System of Particles and Rigid Body; Gravitation). Gravitation is part of that group.

No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed.

Mechanical Properties of Solids.

SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works.

- Ch 7 NCERT book
- 17 marks, Units IV-VI together
- 3 quick checks
- Using the approximation formula g(h) = g(1 - 2h / R) when height is comparable to R . Use the exact formula g(h) = g / (1 + h / R)² whenever h is not significantly smaller than the radius of Earth.
- Forgetting the negative sign in gravitational potential energy . Always write V(r) = -G M m / r when reference is at infinity, because gravity is an attractive force.
- Confusing escape speed with orbital speed . Remember that escape speed is √2 times the orbital speed near the Earth's surface: vₑ = √2 vₒ.

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