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Homework Help: Universal Gravitation

  1. Oct 1, 2006 #1
    At the Earth's surface a projectile is launched straight up at a speed of 10.1 km/s. To what height will it rise?
    Universal gravitational constant = 6.673e-11 N m^2/kg^2
    Radius of the earth = 6.370e+6 m
    Mass of the earth = 5.980e+24 kg

    I know to use the equation U= - (Gm1m2)/ r
    I also need to take into consideration that r is the radius of the earth and the object is launched at the surface of the earth. However how am I suppose to solve for height when their is no mass of the projectile and what do I do with the speed of the projectile. I originally thought I should consider that U=mgy but that got me nowhere. Any help will be appreciated I'm literally teaching this to myself.
  2. jcsd
  3. Oct 1, 2006 #2
    what do you use potential energy for in physics? what are the units of P.E. what other formual has the same units?
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