Finding the period of the satellite's orbital motion

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SUMMARY

The discussion focuses on calculating the period of a satellite's orbital motion using the equation mg = mv²/r. The user derives the formula T = 2πr/sqrt(gr) but is confused by the correct answer, T = 2πr/R * sqrt(r/g). The key distinction lies in the gravitational acceleration, g, which varies with distance from the Earth's center, necessitating the use of R, the Earth's radius, in the correct formula. Understanding this variation is crucial for accurate calculations in orbital mechanics.

PREREQUISITES
  • Understanding of Newton's law of gravitation
  • Familiarity with circular motion equations
  • Knowledge of angular velocity and its relationship to period
  • Basic calculus for deriving equations
NEXT STEPS
  • Study the concept of gravitational acceleration variation with distance from the Earth's center
  • Learn about orbital mechanics and Kepler's laws of planetary motion
  • Explore the derivation of the orbital period formula for satellites
  • Investigate the effects of altitude on satellite motion and gravitational forces
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Students in physics, aerospace engineers, and anyone interested in understanding satellite dynamics and orbital mechanics.

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Homework Statement


Screen Shot 2019-03-17 at 3.50.12 PM.png

I want to find the period of the satellite.

Homework Equations



mg = mv^2/r

The Attempt at a Solution



I derive the equation
mg = mv^2/r
v = sqrt(gr)
v = ωr and ω = 2π/T

T = 2π/ω = 2πr/v

Then, T = 2πr/sqrt(gr)

But the answer is 2πr/R * sqrt(r/g). I don't know why? Is there anyone can give an explanation to me why it is not correct.
 

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Hi,

From the text: ##g## at the surface is not ##g## far away ...
 

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