Chapter 9: Gravitation Application Questions | science Class 9 CBSE

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Chapter 9: Gravitation Application Questions | science Class 9 CBSE | ByteNotes.in

Application Question

Concept in a practical situation

Application

Question 1

Applied Concept

Q1. State Newton’s Law of Universal Gravitation. Derive the expression for force.

Every mass attracts every other mass with a force.
Force ∝ product of masses (m₁m₂), ∝ 1/distance² (1/r²).
F = G × (m₁ × m₂) / r²
G is the universal gravitational constant.
It is applicable everywhere in the universe.

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Application Question

Concept in a practical situation

Application

Question 2

Applied Concept

Q2. What is the importance of the value of G?

G = 6.674 × 10⁻¹¹ N·m²/kg².
It determines gravitational force between two 1 kg masses 1 m apart.
It is a very small number → weak force.
Essential in calculating planetary motions.
Fundamental to astrophysics and cosmology.

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Application Question

Concept in a practical situation

Application

Question 3

Applied Concept

Q3. Define mass and weight. State their differences.

Mass: amount of matter, constant, measured in kg.
Weight: force due to gravity, variable, W = mg.
Mass is scalar, weight is vector.
Mass remains same everywhere; weight changes with g.
Mass measured with balance; weight with spring balance.

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Application Question

Concept in a practical situation

Application

Question 4

Applied Concept

Q4. Derive the formula for acceleration due to gravity (g).

Using F = G × (M × m)/R² and F = mg.
Equating: mg = G × (M × m)/R².
g = G × M / R².
Where M = mass of Earth, R = radius of Earth.
g = 9.8 m/s² on Earth’s surface.

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Application Question

Concept in a practical situation

Application

Question 5

Applied Concept

Q5. A 50 kg person stands on Moon. What is his weight there?

Moon’s g = 1/6 of Earth = 9.8/6 ≈ 1.63 m/s².
Weight = mg = 50 × 1.63 = 81.5 N.
Mass remains 50 kg.
Weight is much lower than on Earth (490 N).
Explains ease of jumping on Moon.

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Application Question

Concept in a practical situation

Application

Question 6

Applied Concept

Q6. What is Archimedes’ Principle? State two applications.

It states: upward buoyant force = weight of displaced fluid.
Used to find purity of metals (e.g., gold in crown).
Used in hydrometers to measure fluid density.
Used in design of ships and submarines.
Important in fluid mechanics and engineering.

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Chapter sections

Chapter 9: Gravitation | Application Questions

Q1. State Newton’s Law of Universal Gravitation. Derive the expression for force.

Q2. What is the importance of the value of G?

Q3. Define mass and weight. State their differences.

Q4. Derive the formula for acceleration due to gravity (g).

Q5. A 50 kg person stands on Moon. What is his weight there?

Q6. What is Archimedes’ Principle? State two applications.

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