Overview

We will cover SSC Gravitation in very creative way as required in SSC Exam. In this topic we will cover gravitation concept with PYQ questions. All questions are provided with topic so that we know what is important for us in this topic. You can also share feedback about this topic.

How we do?

• First we will learn the concept with picture explanation.
• All important questions attach with the topic.
• we use flash card for better understanding the concept and learn the fact.
• At last we use the quiz to check out our performance.

Universal Law of Gravitation

• Every point mass attracts every other point mass by a force acting along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between them.
• Gravitational Constant (G): Value is 6.67×10−11 Nm2/kg2 6.67×10−11Nm2/kg2. Discovered by Henry Cavendish in 1798.

• Description: The force between two charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
• S.I unit of charge: Coulomb (important directly asked by examiner)

Type of questions can be asked from this topic

1. Doubling the distance (r) between two charges reduces the electrostatic force (F) to one-fourth: F∝/r2​.
2. Tripling the magnitude of one charge (q) triples the electrostatic force: F∝q1​×q2​.
3. The S.I. unit of charge is the Coulomb.
4. Both gravitational and electrostatic forces are conservative: work done in a closed path is zero.
5. Halving the distance between two charges quadruples the electrostatic force: F∝/r2​.
6. Doubling the magnitude of both charges quadruples the electrostatic force: F∝q1​×q2​.
7. Opposite charges attract each other: if one charge is positive and the other is negative, the force is attractive.
8. The electrostatic force is undefined at a distance of zero:
9. A characteristic of conservative forces is that work done in a closed path is zero.
10. If the distance between two charges is tripled and one of the charges is doubled, the electrostatic force becomes 2/9​ of the original force: just use the formula

Similarities between Gravitational and Electrostatic Forces

• Both are non-contact and conservative forces.
• Work done is independent of the path.
• Work done in a closed path is zero.

Kepler’s Planetary Laws

1. Law of Orbits: Planets move in elliptical orbits with the Sun at one focus.

2. Law of Areas: A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.

3. Law of Periods: The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

Difference between Mass and Weight

Property	Mass	Weight
Nature	Intrinsic property	Force due to gravity
Quantity	Scalar	Vector
Unit	Kilogram (kg)	Newton (N)
Changes	Constant	Varies with gravity

Weight: force by which Earth attracts a mass
Force = m x a Weight = m x g
Here mass is constant but gravity differs

Variation in gravity

Aspect of Gravity	Explanation
Gravity at Poles vs Equator	Gravity is stronger at the poles than at the equator.
Gravity with Altitude	As altitude increases, gravity decreases.
Gravity on the Moon vs Earth	The moon’s gravity is 1/6th that of Earth’s.

Vary g = 9.8 m/s ~ 10 m/s
Different from “G”
which is constant

Type of questions can be asked from the above topic

1.Which Kepler’s Law states that planets move in elliptical orbits with the Sun at one focus?
Answer: Kepler’s First Law (Law of Orbits).
2. According to Kepler’s Second Law, what remains constant as a planet orbits the Sun?
Answer: The area swept out by the line segment joining the planet and the Sun in equal intervals of time (Law of Areas).
3. How does the cube of the semi-major axis of a planet’s orbit relate to the square of its orbital period?
Answer: The cube of the semi-major axis is directly proportional to the square of the orbital period (Kepler’s Third Law – Law of Periods).
4. What is the difference between mass and weight?
Answer: Mass is the measure of the amount of matter in an object, while weight is the force exerted on an object due to gravity.
5. How does weight change with the strength of the gravitational field?
Answer: Weight increases with the strength of the gravitational field and decreases as the gravitational field weakens.
6. What is the SI unit of mass?
Answer: Kilogram (kg).
7. What force is responsible for the weight of an object?
Answer: Gravitational force.
8. How does the distance between two objects affect the gravitational force between them?
Answer: The gravitational force decreases as the square of the distance between the two objects increases (inverse square law).
9. What law explains the proportional relationship between gravitational force and the product of two masses?
Answer: Newton’s Universal Law of Gravitation.
10. How does the weight of an object on the Moon compare to its weight on Earth?
Answer: The weight of an object on the Moon is about one-sixth of its weight on Earth due to the Moon’s weaker gravitational field

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