Class 9 Science — Chapter 9: GRAVITATION
Chapter 9: GRAVITATION is a chapter in Class 9 Science (NCERT), part of the CBSE NCERT curriculum followed by over 25 million students across India. This chapter covers 8 topics including Centripetal Force and Gravitation, Universal Law of Gravitation, The Gravitational Constant (G). BrainWeave provides free AI-powered explanations — by voice or text, in Hindi or English — with no signup required.
What you'll learn
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▸Centripetal Force and Gravitationcentripetal forcecircular motionorbittangentmoon
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▸Universal Law of GravitationCore conceptuniversal lawproportionalproduct of massesinverse square lawgravitational force
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▸The Gravitational Constant (G)Core conceptuniversal gravitational constantG valueN m² kg⁻²Henry Cavendishproportionality
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▸Calculating Gravitational ForceCore conceptcalculate forceF = G Mm/d²newtonsmassdistance
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▸Importance of the Universal Lawcelestial motiontidesplanetsorbitphenomena
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▸Free FallCore conceptfree fallgravity alonefalling objectsdownward motionacceleration
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▸Acceleration Due to Gravity (g)Core conceptacceleration due to gravitygg = GM/R²9.8 m/s²independent of object mass
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▸Variation in the Value of gvariation of gpolesequatorEarth's radiusnon-spherical
Chapter Summary
Understand that gravitation provides the centripetal force required for celestial bodies like the moon to orbit the Earth in a circular path. Recognize that without this force, an object in circular motion would move in a straight line tangent to the path.
State and understand Newton's Universal Law of Gravitation, including the direct proportionality to the product of masses and the inverse square relationship with the distance between the centers of the objects.
Define the universal gravitational constant 'G', state its accepted value (6.673 × 10⁻¹¹ N m² kg⁻²), and identify its SI unit. Understand that 'G' is a constant of proportionality that is the same everywhere in the universe.
Apply the formula F = G * (M*m)/d² to calculate the magnitude of the gravitational force between two objects, given their masses and the distance between them.
Explain key natural phenomena that are accounted for by the universal law of gravitation, such as the force binding us to Earth, the motion of planets and moons, and the occurrence of tides.
Define 'free fall' as the motion of an object solely under the influence of Earth's gravitational force, resulting in a constant downward acceleration independent of the object's mass.
Understand that 'g' is the acceleration experienced by an object in free fall. Derive and use the formula g = G*M/R² to show that 'g' depends on the mass and radius of the Earth, and calculate its approximate value (9.8 m/s²).
Explain why the acceleration due to gravity (g) is not perfectly constant across the Earth's surface, specifically why it is greater at the poles and lesser at the equator due to the Earth's shape.
Practice Questions from this Chapter
Tap "Get Solution" on any question to ask our AI tutor.
- Explain how gravity keeps planets orbiting. Get Solution →
- Describe what causes Earth's ocean tides. Get Solution →
- Compare gravity on Earth versus the Moon. Get Solution →
- Who is credited with grasping that the same force responsible for a falling apple also keeps the moon in orbit around the Earth? Get Solution →
- What is the force that causes acceleration and keeps a body moving along a circular path, acting towards the center? Get Solution →
- According to the Universal Law of Gravitation, the force between two objects is inversely proportional to what? Get Solution →
- What does the symbol 'G' represent in the equation F = G(M×m)/d²? Get Solution →
- Who experimentally determined the value of the universal gravitation constant, G? Get Solution →
Did you know?
- 💡 Your weight on Mars would be about one-third of your weight on Earth.
- 💡 Gravity is so powerful near a black hole that not even light can escape its pull.
- 💡 Astronauts on the International Space Station continuously fall around Earth, creating weightlessness.
- 💡 Earth's gravity is slightly weaker at the equator because the planet bulges there.
- 💡 Gravitational waves are ripples in spacetime, recently detected from colliding black holes.
Frequently Asked Questions
How many topics are covered in this chapter?
This chapter covers 8 key topics: Centripetal Force and Gravitation, Universal Law of Gravitation, The Gravitational Constant (G), Calculating Gravitational Force, Importance of the Universal Law, and more. The BrainWeave AI tutor explains each one with examples.
Is Chapter 9: GRAVITATION important for board exams?
Class 9 is a foundation year. Mastering this chapter now will help you build strong fundamentals for the higher classes.
Can I get NCERT solutions for this chapter in Hindi?
Yes. BrainWeave's AI tutor supports Hindi, English, and Hinglish for both voice and text chat. Just ask your question in your preferred language.
Is BrainWeave free for Class 9?
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