# Gravitation Class 9 Notes CBSE Science Chapter 10

Hey there! If you're looking for some helpful notes for your CBSE NCERT Class 9 Science class, we've got you covered! Our notes cover all the important topics from Chapter 10 Gravitation, including physics, chemistry, and biology. We've put together an overview of all the key concepts and topics from the NCERT TextBooks, so you can easily understand everything you need to know. Our Chapter Notes are organized by topic, so you can quickly find explanations for Gravitation, Universal Law of Gravitation, Free Fall, Acceleration Due to Gravity (g), Difference between G and g, Mass and Weight, and Weight of an Object on the Surface of the earth. We hope you find our notes helpful!

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**will guidance students understand the topics ,concepts and themes covered in all the chapters of Ncert Text book of 9th***CBSE Class 9th Science Chapter Wise Notes*## Gravitation Forced

### Gravitational Forces

All objects in this universe attract each other, this force of attraction is called Gravitational Force

### Newton observations

why does Apple fall on Earth from a tree? Because earth attracts it towards itself.

Can Apple also attract the farth?

Yes, it also attracts the earth as per Newton's third laws [ Every action has an equal and opposite reaction] But the mass of earth is much larger than apple therefore forth never move towards it.

### Universal Law of Gravitation :

Sir Issac Newton in 1684 Proposed a law about force of attraction between the two objects in

the universe which is known as newton's Law of gravitation.

### According to this law

Every object attracts every. other object.

This force is directly proportional to product of their masses force is inversely Proportional to the Square of distance between them.

let my and my be the masses of two objects and distance d then force of attraction between them Fd my xm Fd (1)-

from above equations, we can write as da F= Gi mama ushere Gi is gravitational Constant.

Sing Value of G₁ = 6-673 x 10" Nm² kg found out by Henry Cavendish]

Most IMP

**1 mark Pooch sakte h**

## Importance of Universal Low of Gravitation:

(1) The force that binds us to the Earth. (1) The motion of moon around the forth. The motion of earth around the Sun. (N) The tides due to moon in the Sea.

**Q.What is Free Fall?**

A.whenever objects fall towards earth due to earth's gravity and no other force is acting upon it. the object is said to be in Free Fall. Dusing this free fall direction do not change but Velocity continuously changes which is called Acceleration due to gravity. •Denoted by g SI unit = mis (Some as acceleration)

### Value of 'g

on the Surface of earth s we know that force acting on an object F--(7) No man of earth F= me mass of object

R= radius of object.

we also know from 2nd tow of motion

F mg F=ma, here a=g)

From eqn () and (1), we have

mxg = GMem R

R

when body is at distance 'r' from Centre of earth then.

9-GM parts of Value of 'g' may be Vary at different parts of earth- From the squelch 9= GM, it is clear that value of g depends on & means distance of object from earth's cerere Because shape of earth is not a perfect sphere. It is flat at poles and bulged out CTE BET) of the equator. See the value of 'g' is gavater at the poles. and lesser at the equator But for Convenience we take gas constant. Calculation of 9: 24 = 9-GM R

Difference between Gt and (Important)"

Gravitation Constant (G) Gravitational acceleration (g)

14s value is 6-644x1" Ns value is 9-8 mle

Nm /kg.

Its values mains Constant everywhere Varius places. Hs unit is Nn²/kg Hs unit is m It is Scaly quantity 14 is a vector quantity E

Its valur varies at Equation of motion when an object is falling freely towards earth or than vertically ups

(Important)

Case when an object is falling towards earth with Initial Velocity (u), then Vu+gt

(here a=g) Case an object is falling from rest position means initial velocity (u=0).

v-agh

Vu S-ut-gt

Vagh

Case- then an object is thrown vertically upward's with initial ve bity (u), then gravitational acceleration (g) will be negative motion opposite g act karega thot's why Reigate sign.

Mass & Mass of an object is the measure of Hs inertia.

S1 unit Kilogram (kg) Mass is a scalar quantity.

Mass of a body remains constant

• Mass of a body cannot be zero.

### Weight:

The fore by which an object is attracted towards the Centre of earth is Called Weight of that object. We know, Force = mxa F= meg (as a g). from above definition, this ferre is weight = mxg St. unit Newton (ND. vector quantity.

Distinguish between Mass and weight [Important]

### Mass

Mass is inertia of object weight = mass x acceleration The total quantity of matt Gravitational fere by which in an object is called mass earth attract an object is Called weight

3 Mass of an object semaine weight of object is different at different places

Measurement of mase is Measurement of weight is done by using beam balance done by using spring balance-

Mass can not be zero. weight can be Zero if g is zero. weight of an Objection Moon : (Proof/derivation tight of an object on earth.

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