Chapter 10
Gravitation
Complete chapter resources for CBSE Class 9 Science — topic breakdown, key formulas, sample questions, previous year board questions, and instant AI question paper generation.
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- Universal law: F = G × (m₁ × m₂) / d²
- G (constant): 6.674 × 10⁻¹¹ N m² kg⁻²
- Acceleration due to gravity: g = GM / R² ≈ 9.8 m/s²
- Weight: W = m × g
- Free-fall velocity: v = u + gt ; s = ut + ½gt²
- Buoyant force: F_b = ρ_fluid × V_displaced × g
What this chapter covers
Chapter 10 of CBSE Class 9 Science introduces gravitation — the universal force of attraction between any two objects that have mass. Newton's Universal Law of Gravitation states that this force is directly proportional to the product of the masses and inversely proportional to the square of the distance between them: F = G m₁m₂ / d². The gravitational constant G = 6.674 × 10⁻¹¹ N m² kg⁻² is the same everywhere in the universe, while the acceleration due to gravity g at Earth's surface is approximately 9.8 m/s² and varies with altitude and depth.
The chapter explores free fall — motion under gravity alone with no other forces acting. All objects in free fall experience the same acceleration g regardless of their mass, which is why a stone and a feather fall together in a vacuum. Students apply the three equations of uniformly accelerated motion (with a = g) to solve numerical problems on falling bodies and objects thrown upward. The chapter also distinguishes clearly between mass (an intrinsic property, measured in kg) and weight (a force = mg, measured in Newtons).
The final topics cover thrust, pressure, and Archimedes' principle. Archimedes' principle states that the buoyant force on a submerged object equals the weight of fluid displaced — explaining why ships float and helium balloons rise. The concept of relative density (density of a substance relative to water) ties these ideas together and frequently appears in 2-mark board questions asking students to predict whether an object will float or sink.
What's inside Chapter 10
As per NCERT Class 9 Science (CBSE syllabus)
How this chapter fits in
Useful for setting question difficulty and cross-chapter papers.
Marks & question-type breakdown
Typical pattern based on CBSE Class 9 Science annual exam papers from the last five years.
| Question type | Marks | Typical count | What's usually tested |
|---|---|---|---|
| MCQ / Objective | 1 | 1 | Value of G, g on Moon, condition for floating/sinking |
| Very Short Answer | 2 | 1–2 | Difference between mass and weight, state Archimedes' principle |
| Short Answer | 3 | 1 | Numerical on free fall, derive g = GM/R², calculate buoyant force |
| Long Answer / Numerical | 5 | 0–1 | Multi-step free fall problem or comprehensive Archimedes' application |
| Total (approximate) | 5–7 | 3–4 | Weightage varies across paper sets and schools |
8 sample questions — generated by MarksZen AI
Aligned to CBSE Class 9 Science Chapter 10. Covers all question types across Easy, Medium, and Hard difficulty.
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From CBSE board examinations
Actual questions from past Class 9 Science board papers — Gravitation chapter.
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- All 4 topics of this chapter
- MCQ + short answer + numericals
- Answer key included
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