Gravitation - Class 9 Flashcards
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Questions and Answers

What is gravitation?

The force in which the earth pulls the objects towards itself.

Every object in the universe attracts every other object.

True

What is the universal law of gravitation?

Every object in the universe is attracted to every other object by a force proportional to the product of their masses and inversely proportional to the distance between them.

The formula of the universal law of gravitation is G = _____

<p>m1m2/d^2</p> Signup and view all the answers

What is the SI unit of the gravitational constant 'G'?

<p>Nm^2kg^-2</p> Signup and view all the answers

What is the value of G?

<p>6.67 x 10^-11 Nm^2/kg^2</p> Signup and view all the answers

Gravitational force between small and big objects causes noticeable motion.

<p>False</p> Signup and view all the answers

How does gravitational force hold the solar system together?

<p>It keeps the earth in uniform circular motion around the sun.</p> Signup and view all the answers

What is Kepler's first law?

<p>The orbit of a planet is an ellipse with the Sun at one of the two foci.</p> Signup and view all the answers

What does Kepler's Second Law state?

<p>A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.</p> Signup and view all the answers

What is Kepler's Third Law?

<p>The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.</p> Signup and view all the answers

What does Newton's third law imply in gravitation?

<p>When the mass of a stone is small, the gravitational force produces significant acceleration.</p> Signup and view all the answers

What is free fall?

<p>The motion of a falling object when the only force acting on it is gravity.</p> Signup and view all the answers

The equations of motion for freely falling bodies are v = u + gt, h = ut + _____, v^2 = u^2 + 2gh.

<p>1/2ft^2</p> Signup and view all the answers

What is mass?

<p>The quantity of matter contained in a body.</p> Signup and view all the answers

What is weight?

<p>The force with which a body is attracted towards the centre of the earth.</p> Signup and view all the answers

What is the weight of an object on the moon?

<p>About one-sixth of its weight on the earth.</p> Signup and view all the answers

Study Notes

Gravitation

  • Gravitation is the force exerted by the Earth that pulls objects towards its center, acting downward and responsible for holding the atmosphere.

Universal Attraction

  • Every object in the universe attracts every other object, regardless of size. Smaller masses result in gravitational forces that are often undetectable.

Universal Law of Gravitation

  • This law states that the gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Gravitational Formula

  • The formula for the universal law of gravitation is expressed as ( F = \frac{G \cdot m_1 \cdot m_2}{d^2} ).

SI Unit of Gravitational Force

  • The SI unit of the gravitational constant ( G ) is ( \text{Nm}^2/\text{kg}^2 ).

Value of G

  • The value of the gravitational constant ( G ) is approximately ( 6.67 \times 10^{-11} \text{Nm}^2/\text{kg}^2 ).

Gravitational Force Between Different Sizes

  • Gravitational attraction exists between all objects, but the force is often too small to cause noticeable motion, especially between objects of vastly different sizes.

Solar System Dynamics

  • The gravitational force between celestial bodies, such as the Sun and Earth, is significant due to their large masses, keeping planets in uniform circular motion around the Sun.

Kepler's First Law

  • The orbit of a planet around the Sun is elliptical, with the Sun located at one of the foci of the ellipse.

Kepler's Second Law

  • A line segment connecting a planet and the Sun sweeps out equal areas during equal intervals of time, indicating varying speeds; planets travel faster when closer to the Sun.

Kepler's Third Law

  • The square of a planet's orbital period is proportional to the cube of the semi-major axis of its orbit, expressed as ( r^3 \propto T^2 ).

Newton's Third Law and Gravitation

  • When a small mass, such as a stone, falls to Earth, it experiences significant acceleration due to gravity, illustrating the principles of Newton's third law.

Free Fall

  • Free fall is the motion of an object falling under the sole influence of gravity, with no other forces acting on it.

Equations of Motion for Free Fall

  • Key equations include:
    • ( v = u + gt )
    • ( h = ut + \frac{1}{2}gt^2 )
    • ( v^2 = u^2 + 2gh )

Mass

  • Mass is defined as the quantity of matter in a body, measured in kilograms, and is a scalar quantity. An object's mass cannot be zero.

Weight

  • Weight is the force of gravity on an object, calculated as ( F = ma ), with 1 kg having a weight of approximately 9.8 newtons. Unlike mass, weight is a vector quantity.

Weight on the Moon

  • The weight of an object on the Moon is roughly one-sixth of its weight on Earth, demonstrating how gravitational pull differs by celestial bodies.

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Description

This quiz covers essential concepts of gravitation for 9th-grade students. It includes definitions and principles introduced by Newton concerning the gravitational force and its impact on objects. Perfect for helping students review and understand gravity's role in the universe.

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