Gravitation One Shot Notes with Most Important Questions -

Gravitation Beginner to Advance Notes | Complete Theory, MCQs, HOTS, Case Study & Questions Answers

Table of Contents ( Gravitation One Shot Notes )

Introduction to Gravitation
What is Gravitation?
History of Gravitation
Newton’s Universal Law of Gravitation
Importance of Gravitation
Free Fall
Acceleration Due to Gravity (g)
Mass and Weight
Difference Between Mass and Weight
Thrust and Pressure
Buoyancy
Archimedes’ Principle
Relative Density
Important Formulae
Important Abbreviations
Key Points for Revision
MCQs
HOTS Questions
Case Study Questions
Short Answer Questions
Long Answer Questions
Exam Tips
Conclusion

Introduction to Gravitation ( Gravitation One Shot Notes )

Gravitation is one of the most important concepts in Physics. It explains why objects fall towards the Earth and why planets revolve around the Sun. Moreover, gravitation plays a major role in our daily lives. ( Gravitation One Shot Notes )

गुरुत्वाकर्षण (Gravitation) भौतिक विज्ञान का एक महत्वपूर्ण विषय है। यह बताता है कि वस्तुएँ पृथ्वी की ओर क्यों गिरती हैं तथा ग्रह सूर्य के चारों ओर क्यों घूमते हैं। इसके अलावा, यह हमारे दैनिक जीवन में भी महत्वपूर्ण भूमिका निभाता है।

What is Gravitation?

English

Gravitation is the force of attraction between any two objects having mass.

Hindi

द्रव्यमान वाली किन्हीं दो वस्तुओं के बीच लगने वाले आकर्षण बल को गुरुत्वाकर्षण कहते हैं।

Examples

Apple falling from a tree
Moon revolving around Earth
Earth revolving around the Sun
Rain falling towards Earth

History of Gravitation ( Gravitation One Shot Notes )

Sir Isaac Newton and the Falling Apple

According to a famous story, Newton observed an apple falling from a tree. As a result, he started thinking about the force that pulled the apple towards Earth.

Subsequently, he proposed the Universal Law of Gravitation.

Hindi

आइज़ैक न्यूटन ने पेड़ से गिरते हुए सेब को देखकर गुरुत्वाकर्षण के सिद्धांत पर विचार किया। इसके बाद उन्होंने सार्वत्रिक गुरुत्वाकर्षण का नियम प्रस्तुत किया।

Newton’s Universal Law of Gravitation

Statement

Every object in the universe attracts every other object with a force.

This force:

Is directly proportional to the product of their masses.
Is inversely proportional to the square of the distance between them.

Formula

$F = \frac{Gm_1m_2}{r^2}$

Where:

F = Gravitational Force
G = Universal Gravitational Constant
m₁ = First Mass
m₂ = Second Mass
r = Distance between centers

Hindi

ब्रह्मांड की प्रत्येक वस्तु दूसरी वस्तु को आकर्षित करती है। यह बल उनके द्रव्यमानों के गुणनफल के समानुपाती तथा उनके बीच की दूरी के वर्ग के व्युत्क्रमानुपाती होता है।

Importance of Gravitation ( Gravitation One Shot Notes )

Gravitation is responsible for:

1. Falling of Objects

Objects fall towards Earth because of gravity.

2. Planetary Motion

Planets revolve around the Sun due to gravitational force.

3. Tides

Ocean tides occur due to the gravitational pull of the Moon.

4. Atmosphere

Earth’s gravity holds the atmosphere around it.

Hindi

गुरुत्वाकर्षण के कारण:

वस्तुएँ पृथ्वी पर गिरती हैं।
ग्रह सूर्य की परिक्रमा करते हैं।
समुद्र में ज्वार-भाटा आता है।
पृथ्वी का वायुमंडल बना रहता है।

Free Fall ( Gravitation One Shot Notes )

When an object falls towards Earth only under the influence of gravity, the motion is called free fall.

Examples

Falling stone
Falling fruit
Raindrops

Hindi

जब कोई वस्तु केवल गुरुत्वाकर्षण बल के प्रभाव में पृथ्वी की ओर गिरती है, तो उसे मुक्त पतन (Free Fall) कहते हैं।

Acceleration Due to Gravity (g)

The acceleration produced in a freely falling object is called acceleration due to gravity.

Symbol

Value

$g = 9.8\ m/s^2$

Formula

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

Hindi

मुक्त रूप से गिरती वस्तु में उत्पन्न त्वरण को गुरुत्वजनित त्वरण कहते हैं।

Equations of Motion for Free Fall

First Equation

$v=u+gt$

Second Equation

$s=ut+\frac{1}{2}gt^2$

Third Equation

$v^2-u^2=2gs$

Mass

Mass is the amount of matter present in an object.

Characteristics

Constant everywhere
Scalar quantity
SI Unit = Kilogram (kg)

Hindi

किसी वस्तु में उपस्थित पदार्थ की मात्रा को द्रव्यमान कहते हैं।

Weight

Weight is the gravitational force acting on a body.

Formula

$W=mg$

SI Unit

Newton (N)

Hindi

किसी वस्तु पर लगने वाला गुरुत्वाकर्षण बल उसका भार कहलाता है।

Difference Between Mass and Weight

Mass	Weight
Amount of matter	Force of gravity
Constant	Changes with location
Scalar	Vector
kg	Newton

Thrust and Pressure

Thrust

Force acting perpendicular to a surface.

Formula

$Thrust = Force$

Hindi

किसी सतह पर लंबवत लगाया गया बल थ्रस्ट कहलाता है।

Pressure

Pressure is force acting per unit area.

Formula

$P=\frac{F}{A}$

SI Unit

Relative Density

Relative Density = Density of Substance ÷ Density of Water

Formula

$RD=\frac{\rho_s}{\rho_w}$

Hindi

किसी पदार्थ के घनत्व और जल के घनत्व के अनुपात को आपेक्षिक घनत्व कहते हैं।

Important Formulae

Concept	Formula
Gravitation	F = Gm₁m₂/r²
Weight	W = mg
Pressure	P = F/A
Relative Density	RD = ρs/ρw
Free Fall	v = u + gt
Free Fall	s = ut + ½gt²
Free Fall	v² – u² = 2gs

Important Abbreviations

Abbreviation	Full Form
SI	International System of Units
G	Universal Gravitational Constant
g	Acceleration Due to Gravity
kg	Kilogram
N	Newton
Pa	Pascal
RD	Relative Density
F	Force
W	Weight
M	Mass of Earth
R	Radius of Earth

Key Points for Quick Revision

Every object attracts every other object.

Gravitational force depends on mass and distance.

Value of g on Earth is 9.8 m/s².

Weight depends on gravity.

Mass remains constant.

Pressure increases when area decreases.

A. Work

B. Energy

C. Pressure

D. Velocity

Answer: C

HOTS Questions

HOTS 1

Why do astronauts appear weightless in a spacecraft?

Answer: Because both the spacecraft and astronauts are in free fall around Earth.

HOTS 2

Why is weight less on the Moon?

Answer: The Moon has lower gravity than Earth.

HOTS 3

Why do sharp knives cut easily?

Answer: Smaller area produces greater pressure.

HOTS 4

Why do ships float despite being heavy?

Answer: Buoyant force balances their weight.

HOTS 5

Can mass become zero in space?

Answer: No. Mass remains constant everywhere.

Case Study Based Questions

Case Study

Rahul weighs 600 N on Earth. He travels to the Moon where gravity is one-sixth of Earth’s gravity.

Q1. Will Rahul’s mass change?

Answer: No.

Q2. What happens to his weight?

Answer: It decreases.

Q3. Approximate weight on Moon?

Answer: 100 N

Q4. Why does weight decrease?

Answer: Due to lower gravity.

Q5. Is mass dependent on gravity?

Answer: No.

Short Answer Questions

1. Define gravitation.

Gravitation is the force of attraction between two masses.

2. What is free fall?

Motion under gravity alone is called free fall.

3. Define weight.

Weight is the gravitational force acting on an object.

4. What is buoyancy?

The upward force exerted by a fluid is called buoyancy.

5. What is pressure?

Pressure is force acting per unit area.

Long Answer Questions

1. State Newton’s Universal Law of Gravitation.

Every object attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

2. Differentiate between mass and weight.

Mass is the quantity of matter in a body, whereas weight is the gravitational force acting on it. Mass remains constant, but weight changes with gravity.

3. Explain Archimedes’ Principle.

When a body is immersed in a fluid, it experiences an upward force equal to the weight of the fluid displaced. Therefore, floating and sinking can be explained using this principle.

Exam Tips

Learn all formulas carefully.
Revise definitions daily.
Practice numerical questions.
Understand the difference between mass and weight.
Remember SI units.
Solve MCQs and HOTS regularly.
Focus on Archimedes’ Principle and buoyancy.

Conclusion

Gravitation is a fundamental force of nature. It keeps planets in orbit, causes objects to fall, and helps maintain life on Earth. Furthermore, concepts such as free fall, mass, weight, pressure, buoyancy, and Archimedes’ Principle are frequently asked in school and competitive examinations. Therefore, a clear understanding of gravitation is essential for scoring high marks and building a strong foundation in Physics.

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