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Simple Gravity Problem

  1. Jun 20, 2012 #1
    I am doing a problem which involved determining how fast a rocket was launched off the earth to reach a maximum height.

    I am looking for some assistance with some simple algebra.

    The formula used is;

    Etotal = -Gm1m2/r+0.5m2v^2

    To isolate for v, would my equation be;

    v=sqrt(2(Etotal+(Gm1/r))
     
  2. jcsd
  3. Jun 20, 2012 #2

    Doc Al

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    Staff: Mentor

    OK.

    Not exactly. (You missed an m2 in there.)

    But instead of doing this, express the total mechanical energy at the highest point and compare it to that at the starting point. Then you can make use of energy conservation.
     
  4. Jun 20, 2012 #3
    Thanks for your help!

    I looked over it again and found the answer I was looking for.
     
  5. Jun 20, 2012 #4
    Ok so I rearranged and got the correct answer. I was just wondering if this equation I've attached can be reduced even further?
     

    Attached Files:

  6. Jun 20, 2012 #5

    Doc Al

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    I would combine those fractions using a common denominator.
     
  7. Jun 20, 2012 #6
    Ok, how does this look?
     

    Attached Files:

  8. Jun 20, 2012 #7

    Doc Al

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    Staff: Mentor

    Looks good to me. (You can even put the 2 in the numerator and erase one set of parentheses.)
     
  9. Jun 20, 2012 #8
    Oh ya?

    Thanks for you help.
     
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