PhysicsChapter 1: Gravitation
VARIATION OF g WITH ALTITUDE
Gravitational field strength decreases as altitude above Earth increases because the object becomes farther from Earth’s centre.
Definition
Gravitational field strength decreases as altitude above Earth increases because the object becomes farther from Earth’s centre.
Small Height Approximation
At Earth’s surface: g₀ = GM/R² At height `h` above Earth: distance from centre is: r = R + h Therefore: gh = GM/(R+h)² Dividing by surface value: g_hg₀ = R²R+h² Thus: gh = g₀[RR+h]² As `h` increases: g decreases For `h << R`: **gh ≈ g₀(1 − 2h/R)**
Formula / Key Relation
**gh = GM/(R+h)² or gh = g₀[RR+h]²**
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Sticky Notes · Quick Revision
Height `h`
- Distance from Earth centre = `R+h`
60-second revision
- Gravity does not suddenly end in space.
- It gradually decreases with distance.
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