Finding Density of a Planet Using Period of Orbit

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SUMMARY

The discussion focuses on calculating the density of a planet using the orbital period of a satellite. Given the orbital period T = 1.78 hours (converted to 6408 seconds), the relevant equations include T² = (4π²r³)/(GM) and Density = Mass/Volume. The user expresses confusion about isolating variables and suggests manipulating the equations to find a relationship between density and the orbital parameters. The solution requires understanding the relationship between the period, radius, and gravitational constant.

PREREQUISITES
  • Understanding of gravitational physics, specifically Kepler's laws.
  • Familiarity with the equations of motion in circular orbits.
  • Basic knowledge of algebraic manipulation of equations.
  • Concept of density and volume calculations for spheres.
NEXT STEPS
  • Study the derivation of Kepler's Third Law and its application to satellite motion.
  • Learn how to manipulate equations involving gravitational forces and orbital mechanics.
  • Explore the concept of uniform density in celestial bodies and its implications.
  • Investigate the relationship between orbital radius and period in circular orbits.
USEFUL FOR

Students studying physics, particularly those focusing on gravitational dynamics and orbital mechanics, as well as educators seeking to clarify concepts related to density and satellite motion.

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Homework Statement



A satellite is in a circular orbit very close to the surface of a spherical planet. The period of the orbit is T = 1.78 hours.
What is density (mass/volume) of the planet? Assume that the planet has a uniform density.

Homework Equations



T^{2}=4*PI^2*r^3/G*M
Density = Mass/Volume
Volume of Sphere = 4/3*PI*r^2

The Attempt at a Solution


I converted T into seconds, which I get 6408 seconds,

I have tried to solve for a single variable, but when I put it back into the equation, everything cancels out...

What should I do, I'm just super confused... :(
 
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So we have


T^2=\frac{4\pi^2 r^3}{GM}

and we know V=\frac{4}{3}\pi r^3


So if we divide the equation with T2 by 3, can we somehow factor out (4/3)πr3?
 

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