Have you ever wondered how you can walk on the ground freely ? or when a fruit falls from a tree or something drops from a height, it always heads for the ground? This is exactly what Sir Isaac Newton wondered and offered the world the concept of gravitation. In simple words, Gravitation is the force operating between two objects on the earth. So any thrown object will be attracted toward the earth and will fall on earth. The gravitational force has a very important role which allows us to live in this wonderful world. If gravity disappeared suddenly then we would all start to float immediately. So it is very important to study about Gravitational. And this chapter will help you to understand various laws, various properties of gravitational force along with the application of these laws and properties.
Gravitation is one of the most important chapters from mechanics while preparing for all competitive exam. Because it helps you to understand about gravitational force, field, etc which is the basis of many theories which we study under physics. Gravitation is easy to understand and a high scoring topic. You will get at least one question from this chapter. Gravitation and Electrostatics are conceptually similar to each other so when you study Electrostatics after studying gravitation, you will understand its concepts easily. The Concept of Gravitation and other chapters of mechanics are mixed in miscellaneous questions which are asked in competitive exams.
So we will discuss step by step about important topics from this chapter followed by an overview of this chapter.
Then we will understand important formulas from this chapter. Remembering these formulas will increase your speed while questionsolving.
Gravitation Topics
The universal law of gravitation.
Acceleration due to gravity
Kepler's laws of planetary motion.
Gravitational potential energy; gravitational potential.
Escape velocity. Orbital velocity of a satellite. Geostationary satellites.
Overview of Gravitation
In this chapter, you will learn about one of the fundamental force which is a gravitational force. You will also learn to calculate its magnitude with the help of formula that we get from Newton's Law of Gravitation. Now Let's try to understand the gravitational force with the help of Newton's Law of Gravitation
Newton's Law of Gravitation
Gravitational force is an attractive force acting between two masses and separated by a distance r. This force is directly proportional to the and inversely proportional to .
After studying that Gravitation force operates between any two objects on the earth, You may wonder and ask why not all bodies attract each other and stick together due to gravitational force. So answer to this question is that Gravitational Force is the weakest among all the four fundamental forces known to us till now. Let Suppose 2 similar ball of mass 1 kg are placed 1m apart then the gravitational force acting between them is simply G which is equal to As you see this is a very negligible attractive force.
In this chapter, you will learn about various concept regarding acceleration due to gravity (g) with its definitions and suitable example.
Height, Depth, Shape of earth, Rotation of earth are the important factors which affect the value of g.
Let's have a look at how g value changes due to the shape of the earth.
Radius of equator
Radius of pole
Equatorial radius is about 21 km longer than the polar radius.
So
In fact
Or we can say that Weight increases as the body are taken from equator to pole.
You will also learn about satellites and their motion in space. You will also learn to calculate their orbital velocity, their escape velocity, etc.
Gravitational force
Acceleration due to gravity (g)
Variation in 'g' with height
Variation in 'g' with depth
Variation in 'g' due to Rotation of earth
Gravitational field Intensity
Where F=Gravitational force
Gravitational Potential
or
Work done against gravity
Escape velocity
Escape energy
Kepler's 2nd law
Kepler's 3rd law
or
Energy of satellite
Make a plan to prepare for this chapter and Stick to a Timetable.
Study the concept first and then start solving questions. Don't go through question directly without knowing the concept.
Solve previous year question of various exam from this chapter.
Use smart methods to solve questions.
For Gravitation, chapter concepts in NCERT are enough but you will have to practice lots of questions including previous year questions and you can follow other standard books available for competitive exam preparation like Concepts of Physics (H. C. Verma) and Understanding Physics by D. C. Pandey (Arihant Publications).
Chapters No. 
Chapters Name 
Chapter 1 

Chapter 2 

Chapter 3 

Chapter 4 

Chapter 5 

Chapter 7 

Chapter 8 

Chapter 9 

Chapter 10 

Chapter 11 

Chapter 12 

Chapter 13 

Chapter 14 

Chapter 15 

Chapter 16 

Chapter 17 

Chapter 18 

Chapter 19 

Chapter 20 

Chapter 21 
The mass density of a spherical body is given by ρ (r)= for r ≤ R and ρ (r)=0 for r > R, where r is the distance from the centre. The correct graph that describes qualitatively the acceleration, a, of a test particle as a function of r is
If the Earth has no rotational motion, the weight of a person on the equator is W. Determine the speed with which the earth would have to rotate about its axis so that the person at the equator will weigh W. Radius of the Earth is 6400 km and g=10 m/s^{2}.
1.1×10^{−3 }rad/s
0.83×10^{−3 }rad/s
0.63×10^{−3} rad/s
0.28×10^{−3} rad/s
The variation of acceleration due to gravity g with distance d from centre of the earth is best represented by
(R=Earth’s radius) :