NCERT solutions for class 9 science chapter 10 Gravitation: The main motive of this article is to provide you the NCERT solutions so that you can understand the chapter easily. Through CBSE NCERT solutions for class 9 science chapter 10 Gravitation, you will get the necessary insights into the chapter. Have you ever noticed, When you shake a tree leaf, it falls down? When we drop a pen, it falls. A leaf & pen fall down because of gravitational force due to earth. The solutions for NCERT class 9 science chapter 10 Gravitation are going to provide you the solutions for some important topics of the chapter such as gravitation, free fall, weight, thrust, and pressure, etc. NCERT Solutions are also available class wise and subject wise.
What you are going to learn in NCERT solutions for class 9 science chapter 10 Gravitation?
- We study the gravitational force between two bodies, acceleration due to gravity, free fall, buoyancy force, and relative density.
- 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
Where G is called universal gravitational constant whose value is
- The value of acceleration due to the gravity of earth (g) on an object is given by the equation
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
Where R is the radius of the earth.
- 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:
10.1.1 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
10.4.1 Weight of an Object on the Moon
10.5 Thrust and Pressure
10.5.1 Pressure in Fluids
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 10 Gravitation
Topic 10.1 Gravitation
Q1. State the universal law of gravitation.
The universal law of gravitation states that everybody in the universe attracts every other body by the virtue of its mass. This force is directly proportional to the product of the masses of the two bodies and inversely proportional to the square of the distance between them.
Let there be two bodies of masses m1 and m2 and let the distance between them be r. The gravitational force Fg between them would be given by
where G is the universal gravitational constant and is equal to
Solutions for NCERT class 9 science chapter 10 Gravitation
Topic 10.2 Free fall
Q1. What do you mean by free fall?
We say an object is freely falling when it is dropped from some height and is attracted by the gravitational force of earth only and is under the influence of no other considerable force.
CBSE NCERT solutions for class 9 science chapter 10 Gravitation
Topic 10.4 Weight
Q1. What are the differences between the mass of an object and its weight?
The following are the differences between the mass of a body and its weight
|(i) Mass is the amount of matter contained in the body.
||(i) Weight is the gravitational force experienced by the body.
|(ii) Mass of a body is always constant.
||(ii) Weight of a body depends on the place where it is at.
|(iii) Mass is the measure of the inertia of the body.
||(iii) Weight is the measure of the gravitational force acting on the body.
|(iv) Mass only has magnitude.
||(iv) Since weight is a force it naturally has a direction associated with it as well
|(v) It's SI unit is the kilogram (kg).
||(v) It's SI unit is Newton (kg m s-2)
Q2. Why is the weight of an object on the moon its weight on the earth?
The weight of an object on the moon would be given by
where MM is the mass of the moon, m is mass of the body, rM is the radius of the moon and G is the gravitational constant.
The weight of an object on the Earth would be given by
where ME and rE are the mass and radius of the earth respectively.
The above ratio is approximately equal to 1/6 and this is why the weight of an object on the moon (1/6)th of its weight on the earth.
Q2. What do you mean by buoyancy?
When an object is placed in a fluid it displaces a volume of liquid equal to its own volume. Due to this, the liquid exerts an upward force on the body called the Buoyant force. This tendency of a liquid to exert the upward buoyant force is called buoyancy.
Q3. Why does an object float or sink when placed on the surface of the water?
When an object is placed on the surface of the water it displaces a certain volume of water. If the density of the object is less than that of water the buoyant force due to this displacement of water is equal to the weight of the object and it floats on the surface of the water. If the density of the object is more than the density of water, the volume of water displaced would be equal to the volume of the object itself and the buoyant force acting upwards due to this displacement of water would be less than the weight of the object and the object would sink.
NCERT solutions for class 9 science chapter 10 Gravitation
Topic 10.6 Archimedes' Principle
Q1. You find your mass to be on a weighing machine. Is your mass more or less than ?
The weighing scale shows the reading according to the weight applied to it. The weight on the weighing scale would be slightly less than our weight because there is a small upward force acting on us due to the buoyancy of the atmosphere and the reading would be slightly lower than our actual weight, therefore, our mass must be more than 42 kg.
NCERT free solutions for class 9 science chapter 10 Gravitation- Exercise solutions
Q1. How does the force of gravitation between two objects change when the distance between them is reduced to half?
Let there be two bodies of masses m1 and m2 and let the distance between them be r. The gravitational force F between them would be given by
Let the distance between them be halved by two. The gravitational force between them would now be given by
The force of gravitation between two objects would increase by 4 times if the distance between them is halved.
Q.6.(iii) What happens to the force between two objects, if
As the force between the objects is directly proportional to the product of masses of the objects if the masses of both objects are doubled the force will become four times the initial value.
Q13.(i) A ball is thrown vertically upwards with a velocity of . Calculate
The initial velocity of the ball u = 49 m s-1
Final velocity at the highest point would be v = 0
The magnitude of the acceleration is equal to the acceleration due to gravity g
Acceleration, a = -g = -9.8 m s-2
Let the maximum height to which it rises be s
Using the third equation of motion we have
The ball would rise to a maximum value of 112.5 m.
NCERT Solutions for Class 9 Science- Chapter Wise
NCERT Solutions for Class 9 - Subject Wise
Benefits of NCERT solutions for class 9 science chapter 10 Gravitation
- CBSE NCERT solutions for class 9 science chapter 10 Gravitation are easy to use as you just need to scroll down the article for solutions.
- Here along with NCERT solutions for class 9 science you will also get solutions for NCERT class 9 Mathematics.
- In NCERT solutions for class 9 science chapter 10 Gravitation, you will find exercises solutions and topic wise solutions.
- Solutions of NCERT for class 9 science chapter 10 Gravitation can help you to understand the questions and concepts asked in the exam for science so that you can score well in your exams.