NCERT Solutions for class 11 Physics Chapter 8: Gravitation

NCERT Solutions for Class 11 Physics Chapter 8: Gravitation covers concepts of Kepler’s Planetary Laws of Motion, Newton’s Law of Gravitation, Acceleration Due to Gravity, and its variation. Gravity, also known as Gravitational Force, is the universal force of attraction that helps to keep things together.

Class 11 Physics Chapter 8 Gravitation along with Unit 4 Work, Energy, and Power and Unit 5 Motion of System of Particles and Rigid Body has a weightage of 17 marks in the Class 11 Physics Examination. Gravity is the force that holds us onto the Earth and does not let us fly up into space. Although we barely think about it in our daily lives Gravity is essential to keep the systems operating on the Earth and the Universe.

Download PDF: NCERT Solutions for Class 11 Physics Gravitation

NCERT Solutions for Class 11 Physics Chapter 8

Class 11 Physics Chapter 8 – Basic Concepts

Kepler’s Laws of Planetary Motion: Kepler formulated three laws to describe planetary motion – Law of Orbits, Law of areas, and Law of periods.

1. Law of orbits: All the planets revolve around the sun in an elliptical orbit with the sun being at one of the foci of the ellipse.
2. Law of areas: The speed of a planet varies such that its radius, the vector drawn from the sun to the planet sweeps out equal areas in equal intervals of times.
3. Law of Periods: The square of the time period of revolution of a planet is proportional to the cube of the semi-major axis of the elliptical orbit. \(T^2 \propto r^3\)

Newton’s law of gravitation states that each particle in the universe attracts another particle with a force that is directly proportional to the product of their masses. It is also inversely proportional to the square of the distance that exists between them.

\(F_g = {Gm_1m_2 \over r^2}\)

The gravitational potential is the amount of work done in bringing a body with unit mass from infinity to a point in the gravitational field of a body.

V = \(-GM \over R\)

Escape Velocity is the minimum velocity that is required to project a body vertically upward from the surface of the Earth so that it comes out of its gravitational field.

\(v_{escape} = \sqrt{2GM \over R}\)

Orbital velocity is the minimum velocity required to put a satellite into a given orbit around the Earth.

\(v_{orbital} = \sqrt{GM \over R}\)

Class 11 Physics Chapter 8 Related Guides:

Gravitational Potential Energy	Escape Speed	Earth satellites
Weightlessness	Neptune	Specific Gravity
Value of gravitational constant	Motion of celestial bodies in space	Value of g on moon
Relation between G and g	Specific gravity formula	Universal gravitation formula

Class 11 Physics Study Guides:

NCERT Solutions for Class 11 Physics	Physics Formula	Physics Study Notes
Difference between in Physics	Class 11 Physics Notes	Derivations in Physics
SI Units in Physics	Physics Constants	Relation between articles in Physics

CBSE CLASS XII Related Questions

1.
The figure shows three point charges kept at the vertices of triangle ABC. The net electric field, due to this system of charges, at the midpoint M of base BC will be:
- \( \frac{q}{4 \pi \epsilon_0 l^2} \) pointing along MA
- \( \frac{q}{\pi \epsilon_0 l^2} \) pointing along AM
- \( \frac{q}{2 \pi \epsilon_0 l^2} \) pointing along AM
- Zero
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2.
Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:
- attract with a force \( \frac{F}{2} \)
- repel with a force \( \frac{F}{2} \)
- repel with a force \( F \)
- attract with a force \( F \)
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3.
What is displacement current (\( i_d \))? Considering the case of charging of a capacitor, show that \( i_d = \varepsilon_0 \frac{d\Phi_E}{dt} \). What is the value of \( i_d \) for a conductor across which a constant voltage is applied?
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4.
Two parallel plate capacitors X and Y are connected in series to a 6 V battery. They have the same plate area and same plate separation but capacitor X has air between its plates, whereas capacitor Y contains a material of dielectric constant 4. Calculate the capacitances of X and Y, if the equivalent capacitance of the combination of X and Y is \( 4 \, \mu\text{F} \). Calculate the potential difference across the plates of X and Y.
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5.
Write any two features of nuclear forces.
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6.
If Bohr’s quantization postulate (angular momentum \( = \frac{nh}{2\pi} \)) is a basic law of nature, it should be equally valid for the case of planetary motion also. Why, then, do we never speak of quantization of orbits of planets around the Sun? Explain.
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