Astronomy 105

Escape Velocity

18. Escape velocity (Page 136) (Problem 6-3, Additional Problem Set 8)
    

    The textbook presents this quantity in terms of a proportionality on page 136. In fact it is easier to use the equation from which the proportionality was derived. The equation for the escape velocity from a body of mass M and radius r such as a planet, moon or star is given by:

    

    where r is the distance from the satellite to the planet and G is a fundamental constant of nature, given as G = 6.67 X 10^-11 N m²/kg². As noted under Orbital Velocity above, the newton (N) is a unit of force, but to use this equation you don't need to know that, just be sure that your distances are in meters, and your masses are in kilograms. If so your answer will be in m/s.
    

    Example:

    What is the escape velocity from the Sun? The Sun has a mass of 1.989 X 10³⁰ kg} and radius of 6.9599 X 10⁸ m. (These values can be found in the Data File on page 147.)

    
    

    Note that this is also the escape velocity from the solar system, or the speed a space craft must have to leave the solar system.

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