Satellites
Part of the Mechanics section of Coddy's Physics journey. Lesson 86 of 94.
A satellite on a circular orbit is always falling toward the planet, but moves sideways so fast that it keeps missing it. Gravity points to the centre and is the centripetal force.
Gravity points to the centre; the velocity runs along the orbit.
Set the pull equal to the centripetal force:
GMm/r² = mv²/r ⇒ v = √(GM/r)
The satellite's mass cancels. A lower orbit is faster.
Challenge
A satellite must circle a planet at a speed of 8000 m/s. The planet's GM is 4.0×10¹⁴ m³/s²; call it μ. Find the radius r of its orbit.
Try it yourself
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Mechanics
1Vectors and Newton's Laws
Right TrianglesWhat is a Vector?Adding VectorsAxes and DirectionsVector ComponentsForces Around UsFriction and TensionNewton's First LawNewton's Second LawNewton's Third LawRecap - Net Force2Friction
What is Friction?Static FrictionKinetic FrictionFriction and Newton's LawsRecap - Sliding Crate3Inclined Planes
Forces on an InclineGravity ComponentsFrictionless InclineIncline with FrictionWill It Slide?Recap - Ramp Challenge6Projectile Motion
Independent AxesHorizontal LaunchLaunch at an AngleRange and Max HeightRecap - Hit the Target9Work and Energy
WorkKinetic EnergyWork-Energy TheoremGravitational PEConservation of EnergyPowerRecap - Roller Coaster12Impulse and Momentum
MomentumImpulseConservation of MomentumElastic CollisionsInelastic CollisionsRecap - Air Track15Simple Harmonic Motion
What is SHM?Mass on a SpringThe PendulumSHM GraphsEnergy in SHMRecap - Oscillator