PhysicsChapter 1: Gravitation
Orbital Motion and Orbital Velocity
Orbital motion
Definition
Orbital motion occurs when gravity provides the centripetal acceleration required for an object to continually fall around a massive body.
Important Results
Consider satellite mass `m` in a circular orbit of radius `r` around Earth mass `M`. Gravitational force: Fg = GMm/r² Centripetal force requirement: Fc = mv²/r For circular orbit: GMm/r² = mv²/r Cancel `m`: v² = GM/r Therefore: v = √(GM/r) Orbital speed does **not depend on satellite mass. At larger orbital radius: orbital speed is smaller**
Orbit is Free Fall
A satellite remains in orbit because gravity continuously accelerates it toward Earth while its sideways velocity prevents it from striking the surface.
Formula / Key Relation
**vorbit = √(GM/r)**
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Orbital Motion and Orbital Velocity
Sticky Notes · Quick Revision
ORBIT
- Gravity = centripetal force
- `v = √(GM/r)`
60-second revision
- Higher orbit → lower orbital speed.
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