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Homework help finding fraction of initial mass of rocket and fuel

  1. Oct 14, 2009 #1
    1. The problem statement, all variables and given/known data

    Obviously, we can make rockets to go very fast, but what is a reasonable top speed? Assume that a rocket is fired from rest at a space station in deep space, where gravity is negligible.


    If the rocket ejects gas at a relative speed of 1100 and you want the rocket's speed eventually to be 1.00×10−3 c, where c is the speed of light, what fraction of the initial mass of the rocket and fuel is not fuel

    2. Relevant equations

    v=v(ex)ln(m/m0)
    v1=1100lm(m/m0)



    3. The attempt at a solution

    i think im having trouble finding the final velocity. I did another poblem were the final velocity was 4000 m/s and i got it correct.
     
  2. jcsd
  3. Oct 14, 2009 #2
    The final velocity is 1.00×10−3 c.
     
  4. Oct 14, 2009 #3
    that is what i thought but when i try in on mastering physics i get in incorrect
     
  5. Oct 14, 2009 #4
    Try e100 then e200 and you will see why.
     
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