Page 1: Introduction
Gravitation is the force of attraction between any two bodies having mass.
Earth’s gravity keeps us grounded and governs planetary motion.
This chapter covers universal law, free fall, weight, buoyancy, and numericals.
Page 2: Universal Law of Gravitation
G = 6.67 × 10⁻¹¹ Nm²/kg² (universal constant)
Force proportional to product of masses, inversely proportional to square of distance.
Page 3: Importance of Universal Gravitational Constant G
G determines strength of gravity.
Cavendish experiment measured G.
Very small value → gravitational force weak compared to other forces.
Page 4: Free Fall and Acceleration due to Gravity (g)
When only gravity acts → free fall.
All bodies fall with same acceleration g ≈ 9.8 m/s² (near Earth surface).
g = GM/R² (M = Earth mass, R = radius)
Page 5: Equations of Motion under Gravity
h = ut + (1/2)gt²
v² = u² + 2gh
For downward motion, take g positive (or direction of motion).
Page 6: Mass and Weight
- Mass: Amount of matter (constant, scalar, kg)
- Weight: Force due to gravity W = mg (vector, newton, varies with g)
On moon, weight less but mass same.
Page 7: Variation of g
- g decreases with height (1/r²)
- g decreases with depth
- g maximum at poles, minimum at equator (rotation + shape)
Page 8: Thrust and Pressure
Pressure = thrust / area (N/m² or pascal)
Examples: school bag wide straps, sharp knife.
Page 9: Pressure in Fluids
P = ρgh (ρ = density, h = depth)
Atmospheric pressure decreases with height.
Page 10: Buoyancy and Archimedes’ Principle
Float/sink depends on density.
Page 11: Relative Density
No unit. >1 sink, <1 float.
Page 12: Key Formulas Summary
- F = Gm₁m₂/r²
- g = GM/R² ≈ 9.8 m/s²
- W = mg
- P = F/A = ρgh
- Buoyant force = weight of displaced fluid
Page 13: Practice Questions - Easy (1-10)
- State universal law.
- Value of G.
- Mass vs weight difference.
- g on moon?
- Unit of pressure.
- Archimedes’ principle.
- Why ship floats?
- g at poles vs equator.
- Free fall meaning.
- Relative density formula.
Page 14: Practice Questions - Medium (11-20)
- Gravitational force between two 1 kg masses 1 m apart.
- Weight of 50 kg person on Earth and moon.
- Find g at height R from surface.
- Pressure at 10 m depth in water (ρ=1000 kg/m³).
- Buoyant force on object displacing 2 kg water.
- Velocity after falling 20 m from rest.
- Why sharp needle pierces easily.
- Relative density of object floating half submerged.
- Force on moon due to Earth.
- Explain dams thick at bottom.
Page 15: Practice Questions - Hard (21-30)
- Compare g at height h and depth h.
- Weightlessness in space/orbit.
- Advanced buoyancy numerical.
- Variation of g with latitude.
- Prove buoyant force = weight displaced.
- Free fall from height with air resistance hint.
- Gravitational force inside Earth.
- Ship iron but floats explanation.
- Numerical on pressure + force.
- Kepler’s laws connection hint.
Page 16: NCERT Exercise Types
Numerical on g, weight, buoyancy, pressure.
Page 17: Common Mistakes
- Confusing mass and weight
- Wrong g value or sign
- Forgetting density of water 1000
- Mixing thrust and pressure
- Wrong relative density
Page 18: Previous Year Questions
Weight on moon, buoyancy, universal law, numerical on g.
Page 19: Exam Tips
- Write formula first
- Use g=10 or 9.8 as per question
- Show units
- Explain buoyancy clearly
- Memorise G value and g
Page 20: Quick Revision Sheet
All formulas, values, differences.
Page 21: Real-Life Applications
Tides, satellites, ships, dams, hydrometer.
Page 22: Final Motivation
Chapter 10 complete! Gravitation is beautiful and scoring.
Practice numericals and explanations.
Board Buddy Physics dominating 🦖
Page 23: Extra Numericals
More solved problems.
Page 24: Buoyancy Summary
Float/sink conditions.
Page 25: Variation of g Table
Height, depth, latitude.
Page 26: Universal Law Derivation Hint
From Kepler to Newton.
Page 27: Thank You & Copyright
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