Gravity and Altitude
Part of the Mechanics section of Coddy's Physics journey. Lesson 85 of 94.
Your weight is the Earth's pull on you. Set mg equal to the law of gravitation, and your own mass cancels:
g = GM/r²
At the surface, r is the Earth's radius and g = 9.8 m/s².
g falls with the square of the distance from the centre: r = R + h. Twice as far from the centre, a quarter of the pull.
Twice as far from the centre, a quarter of the pull.
Challenge
A space probe flying away from the Earth measures g = 0.392 m/s², where the surface value is g0 = 9.8 m/s². Find its distance r from the Earth's centre, counted in Earth radii.
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 Force4Kinematics in 1D
Position and DisplacementVelocityAccelerationMotion GraphsEquations of MotionRecap - Braking Car16Gravitation
Law of GravitationGravity and AltitudeSatellitesKepler's LawsGravitational EnergyEscape VelocitySatellite EnergyRecap - Mission to Orbit2Friction
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