# NCERT Solutions for Class 9 Science Chapter 10 Gravitation

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NCERT Solutions for Class 9 Science Chapter 10 Gravitation: When we shake a tree leaf falls down because of gravitational force due to earth. When we drop a pen it falls gown due to gravitation. In NCERT Solutions for Class 9 Science Chapter 10, we study the gravitational force between two bodies, acceleration due to gravity, free fall, buoyancy force, and relative density. Throughout NCERT Solutions for Class 9 Science we will take the acceleration due to the gravity of earth as 9.8ms-2.

NCERT Solutions for Class 9: Universal law of gravitation

The gravitational force of attraction between two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance between the object. That is if two masses M and m are separated by a distance d apart then the gravitational force

$\\F\propto\frac{Mm}{d^2}\\F= G \frac{Mm}{d^2}$

Where G is called universal gravitational constant whose value is

$G= 6.7\times10^{-11}Nm^2Kg^{-2}$

NCERT Solutions: Acceleration due to gravity

The value of acceleration due to the gravity of earth (g) on an object is given by the equation

$g= \frac{GM}{d^2}$

Where M is the mass of the earth and d is the distance between the object and the earth. If the object is on the surface of earth or near to earth then the radius of the earth is approximately =  distance between the object and the earth. Therefor

$g= \frac{GM}{R^2}$

Where R is the radius of the earth.

An important topic of NCERT Solutions for Class 9 Science Chapter 10 is BUOYANCY

We have experienced that it is easy to lift a bucket of water from a well till the surface of the water and above the water weight increase. The less weight inside the water is due to a force exerted by water against the weight of a bucket of water. This force exerted by the liquid is known as upthrust or buoyant force. All the objects experience a force of buoyancy when they are immersed in a fluid. The magnitude of the upthrust (buoyant force) depends on the density of water. Objects of density less than that of a liquid float on the liquid and the objects of density greater than that of a liquid sink in the liquid.

The main topics of NCERT Solutions for Class 9 Science Chapter 10 Gravitation are given here:

10.1 Gravitation

10.1.1 Universal Law of Gravitation

10.1.2 Importance of The Universal Law of Gravitation

10.2 Free Fall

10.2.1 To Calculate The Value Of g

10.2.2 Motion of Objects Under the Influence of Gravitational Force of the Earth

10.3 Mass

10.4 Weight

10.4.1 Weight of an Object on the Moon

10.5 Thrust and Pressure

10.5.1 Pressure in Fluids

10.5.2 BUOYANCY

10.5.3 Why Objects Float Or Sink When Placed on The Surface of Water?

10.6 Archimedes’ Principle

10.7 Relative Density

The difference between mass and weight is also mentioned in NCERT Solutions

What is the difference between weight and mass?

Mass of an object is a measure of inertia. It is the measure of the amount of matter in a body and is constant everywhere. But weight is the force due to gravity. If m is the mass of the object and g is the acceleration due to gravity then weight w=mg. Weight varies according to the distance since g is dependent on distance. The weight of an object in the earth is different from the weight of the same object in the moon since the value of g is different in the moon and Earth. But the mass of the object will be the same in the moon and earth.

## NCERT Solutions for Class 9 Science- Chapter Wise

 Chapter No. Chapter Name Chapter 1 Matter in Our Surroundings Chapter 2 Is Matter Around Us Pure Chapter 3 Atoms and Molecules Chapter 4 Structure of The Atom Chapter 5 The Fundamental Unit of Life Chapter 6 Tissues Chapter 7 Diversity in Living Organisms Chapter 8 Motion Chapter 9 Force and Laws of Motion Chapter 11 Work and Energy Chapter 12 Sound Chapter 13 Why Do We Fall ill? Chapter 14 Natural Resources Chapter 15 Improvement in Food Resources