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VARIATION OF g WITH ALTITUDE
Gravitational field strength decreases as altitude above Earth increases because the object becomes farther from Earth’s centre.
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VARIATION OF g WITH ALTITUDE
What is it?
Gravitational field strength decreases as altitude above Earth increases because the object becomes farther from Earth’s centre.
In simple words
- Gravity does not suddenly end in space.
- It gradually decreases with distance.
Recommended for Class 12
Full school-level explanation
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**
Remember
- gh ≈ g₀(1 − 2h/R)
- gh = GM/(R+h)²
- gh = g₀[RR+h]²
Deeper understanding
Go deeper on VARIATION OF g WITH ALTITUDE: connect the definition to reasons, relationships, exceptions, and exam wording.
Common mistakes
Exam focus
Height `h`
Exam focus
Quick revision
- gh ≈ g₀(1 − 2h/R)
- gh = GM/(R+h)²
- gh = g₀[RR+h]²
- Small Height Approximation: At Earth’s surface: g₀ = GM/R² At height `h` above Earth: distance from centre is: **r = R +
- Formula / Key Relation: **gh = GM/(R+h)²** or **gh = g₀[RR+h]²**
- Gravity does not suddenly end in space.
For long answers on VARIATION OF g WITH ALTITUDE: define clearly → explain the main parts → give one example → state one exam caution.
Exam Focus
Exam Focus
Important points
- gh ≈ g₀(1 − 2h/R)
- gh = GM/(R+h)²
- gh = g₀[RR+h]²
- Small Height Approximation: At Earth’s surface: g₀ = GM/R² At height `h` above Earth: distance from centre is: **r = R +
Important formulas
- gh ≈ g₀(1 − 2h/R)
- gh = GM/(R+h)²
- gh = g₀[RR+h]²
Common exam traps
- Do not use `h` alone as the distance in Newton’s equation.
- Use:
Long question structure
Definition → key parts → example → exam caution
Common Mistakes
Common Mistakes
- Mistake
Do not use `h` alone as the distance in Newton’s equation.
- Mistake
Use:
- Mistake
R + h
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
gh ≈ g₀(1 − 2h/R)
gh = GM/(R+h)²
gh = g₀[RR+h]²
Small Height Approximation: At Earth’s surface: g₀ = GM/R² At height `h` above Earth: distance from centre is: **r = R +
Gravitational field strength decreases as altitude above Earth increases because the object becomes farther from Earth’s centre.
gh = GM/(R+h)²
- Definition
- Gravitational field strength decreases as altitude above Earth increases because the object becomes farther from Earth’s centre.
- Formula
- gh = GM/(R+h)²
- Critical warning
- Do not use `h` alone as the distance in Newton’s equation.
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Exam Practice
Define
Q1. Define VARIATION OF g WITH ALTITUDE.
Explain
Q2. Explain: Small Height Approximation.
Example
Q3. Give one clear example of VARIATION OF g WITH ALTITUDE and say why it fits.
Mistake
Q4. State one common mistake students make about VARIATION OF g WITH ALTITUDE.
Exam note
Q5. Write a short exam note on VARIATION OF g WITH ALTITUDE: definition, two points, one example.
Sources & References
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.