Gravitation | CBSE Class 9 Science | Future Classes
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Explore the Mysteries of Gravitation with Future Classes for CBSE Class 9 Students

CBSE Class 9 Science Chapter Gravitation is a crucial topic that requires a deep understanding. Future Classes is here to help you master this subject with our comprehensive study materials. All resources are created by Anurag, a highly experienced professional. You can download and access our short notes and PDF files to aid your learning. We are proud to provide high-quality educational materials to help you achieve your goals.

Our website offers free PDF downloads of the CBSE Class 9 Science curriculum, including the topic of Gravitation. Our PDFs are clear and concise, making them easy to understand and study from. They are also available in multiple formats, ensuring compatibility with any device. Download our PDFs now and get the best out of your Science studies

CHAPTER-9 GRAVITATION

Gravitation

It is defined as the force of attraction between any two bodies in the universe. The earth attracts (or pulls) all objects lying on or near its surface towards its Centre.

The force with which the earth pulls the objects towards its center is called the gravitational force of the earth or gravity of the earth.

Newton’s Universal Law of Gravitation

Every mass in this universe attracts every other mass with a force which is directly proportional to the product of two masses and inversely proportional to the square of the distance between them.

two object place at a distance d.

Let masses (m1) and (m2) of two objects are distance (d) apart, then force of attraction (F) between them

newton's universal law of gravitation mathmatical expresstion

Where G is a constant and is known as universal Gravitational constant

value of gravitational constant

  • If unit of F is in Newton, m is in kg, d is in meter, then unit of G can be calculated as

unit of univesal gravitational constant

Importance of universal law of gravitation

  • The force that binds us to the earth.

  • The motion of moon around the earth.

  • The motion of earth around the sun.

  • The occurrence tides are due to the gravitational force of attraction of moon.

Free fall

When objects fall towards the earth under the influence of earth’s gravitational force alone, then these are called freely falling objects and such a motion is called free fall.

Gravitational Acceleration

The uniform acceleration produced in a freely falling object due to the gravitational force of earth, is called acceleration due to gravity. It is represented by ‘g’ and it always acts towards the center of the earth.

Value of ‘g’ on the surface of earth

The force acting on an object is

digram of earth with radius R and Me and a object with mass m
find the value of gravitatinal acceleration
find the value of gravitatinal acceleration

Relationship between G and g

relationship between G and g

Difference between G (Gravitational constant) and g (Acceleration due to gravity)

Difference between G (Gravitational constant) and g (Acceleration due to gravity)

​Equation of motion for free fall

The three equations of motion can be applied for the motion of bodies under free fall as follows

Equation of motion for free fall

Where, h is the height from which the object falls, t is the time of fall, u is the initial velocity and v is the final velocity when the body accelerates at g.

  • If an object falls vertically downwards, then acceleration due to gravity is taken as positive.

Mass

The mass of a body is the quantity of matter contained in it. Mass is a scalar quantity which has only magnitude but no direction.

SI unit of mass is kilogram (kg).

  • Mass of a body is constant and does not change from place to place.

  • Mass of a body is usually denoted by the small ‘m’.

  • Mass of a body cannot be zero.

Weight

The force with which an object is attracted towards the center of the earth, is called the weight of the object.

formula for weight

But the force of attraction of earth on an object is called its weight (W). So,

So, weight is the force and its SI unit is Newton (N). It depends on ‘g’ and is a vector quantity.

Difference between Mass and Weight

Mass

  • We can measure mass of an object by its inertia.

  • The total quantity of matter contained in an object is called mass of an object.

  • Mass of the object remains constant at all the places.

Weight

  • Weight = mass × acceleration or m× g.

  • The gravitational force by which earth attracts an object is called weight of the object.

  • Weight of the object is different at different places.

The weight of an object on moon is one-sixth of the weight on earth

The weight of an object on moon is one-sixth of the weight on earth

Thrust

The force acting on an object perpendicular to the surface is called thrust.

Pressure

The effect of thrust per unit area is called pressure.

relation between pressure, force and area

SI unit is newton per meter square or N/m2.

SI unit of pressure is Pascal denoted by ‘Pa’.

Buoyancy

​The upward force experienced by an object when it is immersed into a fluid is called force of buoyancy. It acts in upward direction and it depends on the density of the fluid.

Density

The mass per unit volume is called density of an object.

If M is the mass and V is the volume, then density (d) is

relation between density, mass and volume

Archimedes’ Principle

It states, when a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it.

Relative density

​The ratio of the density of a substance to that of the density of water is called relative density.

formula for relative density

It has no unit.

  • The relative density is greater than 1 then substance will sink.

Our website offers free PDF downloads of the CBSE Class 9 Science curriculum, including the topic of Gravitation. Our PDFs are clear and concise, making them easy to understand and study from. They are also available in multiple formats, ensuring compatibility with any device. Download our PDFs now and get the best out of your Science studies

Gravitation - Chapter 9, CBSE, Class 9

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