How Does Eccentricity Influence Orbital Speed Ratios in Planetary Motion?

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SUMMARY

The discussion focuses on calculating the ratio of orbital speeds at perihelion and aphelion for a planet with an eccentricity of 0.006800 and a semimajor axis of 0.7233 AU. The correct formulas for aphelion (ra = a(1+e)) and perihelion (rp = a(1-e)) distances are emphasized, correcting the initial misunderstanding in the calculation. The final ratio of speeds is derived from the relationship v(p) / v(a) = r(a) / r(p), leading to the conclusion that the user initially miscalculated the distances used in their ratio.

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  • Understanding of orbital mechanics and Kepler's laws
  • Familiarity with the concepts of eccentricity and semimajor axis
  • Knowledge of angular momentum in planetary motion
  • Basic algebra for manipulating equations
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  • Study the derivation of Kepler's laws of planetary motion
  • Learn about the implications of eccentricity on orbital dynamics
  • Explore angular momentum conservation in celestial mechanics
  • Investigate the effects of varying semimajor axes on orbital speed
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Astronomy students, physics enthusiasts, and anyone interested in understanding the dynamics of planetary motion and the influence of orbital eccentricity on speed ratios.

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Homework Statement


A planet has an eccentricity of 0.006800 and a semimajor axis of 0.7233 AU, find the ratio of ortibal speed at perihelion to that at aphelion.


Homework Equations



d=e x a
L=mvrsin\theta

The Attempt at a Solution


I plugged in and solved for the distance between the foci (0.004918)
and then set the angular momentum constants equal to each other:
m v(p) rmin sin\theta=m v(a) rmax sin\theta
the masses and sin\theta cancel out, so
v(p) x r min = v(a) x r max
and so the ratio is:
v(p) / v(a) = r max / r min

r max is the semimajor axis, and r min is the semimajor axis minus the d as found above:
So, it should be .7233/.718382 which gives me 1.00685, but this was incorrect according to my online homework, could you tell me what I did wrong?
 
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The relation vp/va = ra/rp is correct, but ra and rp are the aphelion and perihelion distances, respectively, and are given by ra = a(1+e) and rp = a(1-e).
 

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