Satellite Energy
Part of the Mechanics section of Coddy's Physics journey. Lesson 90 of 94.
On a circular orbit:
K = GMm/(2r), U = -GMm/r, E = K + U = -GMm/(2r)
So U = -2K and E = -K.
In a circular orbit U = −2K, so E = K + U = −K.
A higher orbit has E closer to zero. Raising a satellite takes the energy W = E2 - E1, even though it ends up slower.
Challenge
A satellite on a circular orbit has a total energy of -12 GJ (-1.2×10¹⁰ J). Its engine raises it to a circular orbit 3 times as far from the planet's centre. Measuring the radii in units of the first orbit (r1 = 1, r2 = 3), find the energy W the engine adds.
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