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Homework Help: Gravity problem

  1. Oct 29, 2008 #1
    I have been struggling with this particular problem related to gravity.

    1. The problem statement, all variables and given/known data
    Mercury's orbital speed varies from 38.8 km/s at aphelion to 59.0 km/s at perihelion. If the planet is 6.99x10^10m from the sun's center at aphelion, how far is it at perihelion.

    2. Relevant equations


    Pe= (-Gm1m2)/r2

    Sun mass = 1.99x1030kg
    Sun Mean Radius= 696x10m
    Sun surface gravity=274m/s2
    Sun Mean distance from central body=2.6x1017km

    Mercury mass = .330x1024kg
    Mercury mean Radius = 2.44x106m
    Mercury Surface Gravity = 3.7m/s2
    Mercury Mean dist. from central body = 57.6x106km
  2. jcsd
  3. Oct 29, 2008 #2


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    Homework Helper

    According to Kepler's Law, when a planet is orbiting around the sun its areal velocity remains constant. So what is the formula for the areal velocity?
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