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Rational function helpp needed immedietly

  1. Nov 2, 2009 #1
    rational function helpp needed immedietly !!!!

    1. when astraunauts go into space, they feel lighter. this is because weight decreases as a person rises above earth's gravitational pull according to the formula

    W(h) = We/(1+h/6400)^2

    where We is the person's weight in newtons, at sea level on earth and W(h) is the weight at h km above sea level

    Q) at what range of altitudes will this astraunaut have a weight of less than 10 N?



    2. Relevant equations

    W(h) = We/(1+h/6400)^2

    3. The attempt at a solution

    i attempted it by trying various methods, it will take too long to type it up here and i already have the answer in the book i tried but i could not get that answer

    so please help ! I would really appreciate that . thank you !!
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited: Nov 3, 2009
  2. jcsd
  3. Nov 3, 2009 #2
    Re: rational function helpp needed immedietly !!!!

    W(h) is the weight of the person at a height of h above sea level. For this person to weigh less than 10 newtons, W(h) needs to be less than 10. So set W(h)<10 and solve for h.
     
  4. Nov 3, 2009 #3

    rock.freak667

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    Homework Helper

    Re: rational function helpp needed immedietly !!!!

    Well you basically want to find when W(h)<10


    so just solve for h in

    [tex]\frac{820}{(1+\frac{h}{6400})^2}<10[/tex]
     
  5. Nov 3, 2009 #4
    Re: rational function helpp needed immedietly !!!!

    ok so when i solve that I end up with

    82 (h+1)^2 > 0

    im lost now?
     
  6. Nov 3, 2009 #5
    Re: rational function helpp needed immedietly !!!!

    You didn't solve for h correctly. Hint: multiply both sides by (1+h/6400)2 and then take the square root of both sides.
     
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