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Finding the Density of a given object

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  1. May 30, 2015 #1
    The density of an object equals its mass divided by its volume. The mass of Earth is 6x10e+24 and its radius is 4000 miles (1.61km = 1mile). What is the density of the Earth in kg/m^3?


    V=4/3pi(r)^3. D=M/V


    Converting 4000 to Km, I get 6400. After plugging it into the Volume equation, I end up with approximately 1x10e+12. I divide 6x10e+24 by 1x10e+12, and my result is 6x10e^12. Is this the correct way to do the given problem? My answer sheet from my professor does not state this as any of the answers, and I can't think of any other way to approach this equation.
     
  2. jcsd
  3. May 30, 2015 #2
    The answer should be in kg/m^3.
     
  4. May 30, 2015 #3

    haruspex

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    Your calculation is hard to follw if you do not state the units at every point. The answer is much too high.
    I suspect you erred in converting cu km to cu m.
    What units are the given mass in?
     
  5. May 30, 2015 #4
    The mass of earth is given in 6x10e+24kg, sorry for not posting it earlier!
     
  6. May 30, 2015 #5

    haruspex

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    Ok, but repost your calculation showing units at every step. Omit no steps.
     
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