Gravitational and electric fields

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SUMMARY

The discussion centers on deriving Kepler's Third Law, which states that the square of the orbital period (T) is proportional to the cube of the radius (R) of the orbit. The user attempts to relate the centripetal force acting on a planet in circular motion to gravitational force, using the equation P = 2π√(R^3/GM). The conversation highlights the need to clarify the derivation of the expression for orbital period and the relationship between radial acceleration, orbital speed, and radius.

PREREQUISITES
  • Understanding of Newton's Law of Universal Gravitation
  • Familiarity with centripetal force concepts
  • Knowledge of circular motion equations
  • Basic grasp of Kepler's Laws of planetary motion
NEXT STEPS
  • Study the derivation of Kepler's Third Law in detail
  • Learn about the relationship between gravitational force and centripetal force
  • Explore the concept of radial acceleration in circular motion
  • Investigate the implications of orbital mechanics on planetary motion
USEFUL FOR

Students studying physics, particularly those focusing on celestial mechanics, astrophysics, or anyone interested in the mathematical relationships governing planetary orbits.

confusedpilot
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Homework Statement


By considering the centripetal force which acts on a planet in a circular orbit, show that T^2 is proportional to R~^3 where T is the time taken for one orbit around the sun and R is the radius of the orbit


Homework Equations


I'm thinking keplers third law?



The Attempt at a Solution


C=2piR

P=2piR/ sqrt*GMm/r

rearranged to give P = 2pi sqrt*R^3/GM

Lost now..
 
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confusedpilot said:

P=2piR/ sqrt*GMm/r


Where did that expression come from?


Find an expression for the radial acceleration in terms of the orbital speed and R.

Then use Newton's second law.
 

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