PhysicsChapter 1: Gravitation
Gravitational Field and Field Strength
A gravitational field
Definition
A gravitational field is a region in which a mass experiences gravitational force. Gravitational field strength at a point is gravitational force per unit test mass: g = Fm
Formula
g = Fm**
Direction
For a spherical mass `M`, the gravitational force on test mass `m` at distance `r` is: F = GMm/r² Since: g = Fm therefore: g = GM/r² Gravitational field strength is a vector. Its direction is **toward the attracting mass**.
SI Unit
From: `g = Fm` the unit is: **N kg⁻¹ It is also equivalent to: m s⁻²**
Field Lines
Gravitational field lines around an isolated spherical mass point radially inward. Where lines are closer together, the field is represented as stronger.
Formula / Key Relation
**g = Fm g = GM/r²**
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Gravitational Field and Field Strength
Sticky Notes · Quick Revision
G ≠ g
- `G` → universal constant
- `g` → local field strength
60-second revision
- `g=GM/r²`
- Direction → toward mass.
- Unit → `N/kg`.
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