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Homework Help: Potential energy problem

  1. Apr 29, 2005 #1
    A NASA satellite has just observed an asteroid that is on a collision course with the Earth. The asteroid has an estimated mass, based on its size, of 5.05×109 kg. It is approaching the Earth on a head-on course with a velocity of 619 m/s relative to the Earth and is now 5.15×106 km away. With what speed will it hit the Earth's surface, neglecting friction with the atmosphere?

    I tried Ep + Ek = Ek + Ep, but no luck, is there a problem with my formula?

    Ep = GMm/r r being the distance between the com of the two.
  2. jcsd
  3. Apr 29, 2005 #2

    Doc Al

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    Staff: Mentor

    The formula is OK, assuming you are applying conservation of energy to the asteroid.
    Don't forget the minus sign: Ep = -GMm/r
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