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Rewriting equation

  1. Nov 7, 2011 #1
    1. The problem statement, all variables and given/known data

    This is for a physics problem. I need to solve this for d, but I'm not sure how.

    2. Relevant equations



    3. The attempt at a solution

    I've gotten up to:

    [itex]\frac{2d}{g} = (t - \frac{d}{v})^{2}[/itex]

    When I multiply the right term out, it becomes a mess, everything I do makes it ugly. What should I try doing?

    My main source of confusion is that multiplying that out gives me:

    [itex]t^{2} - \frac{2dt}{v} + \frac{d^{2}}{v^{2}}[/itex]

    While my solution manual gives the last term as:

    (1+v^2)d^2.

    Those are not the same. What gives?
     
    Last edited: Nov 7, 2011
  2. jcsd
  3. Nov 7, 2011 #2

    SammyS

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    If squaring the right hand side makes it too ugly for you, then try taking the square root of both sides. That makes the math a little more challenging,

    You could multiply both sides by v2 then square the right hand side. Maybe not quite so ugly.
     
  4. Nov 7, 2011 #3
    My main problem is that the solution manual I have gives steps that I just don't follow.

    They multiply out (t-d/v)^2 and get (1+v^2)d^2 for the last term. I literally haven't the slightest how it comes to that, I just get plain old d^2/v^2.. and they aren't the same.
     
  5. Nov 7, 2011 #4

    SammyS

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    How about scanning that solution & posting the image?
     
  6. Nov 7, 2011 #5
    Sure thing, gimme a few minutes.
     
  7. Nov 7, 2011 #6
    http://img585.imageshack.us/img585/5854/physicsstone.png [Broken]

    After "square both sides to obtain.." I don't know how they get that. At all.
     
    Last edited by a moderator: May 5, 2017
  8. Nov 7, 2011 #7

    SammyS

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    It's just a typo.

    It could be (1 ÷ v2) d2

    The following lines appear to be correct.
     
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