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Homework Help: Simultaneity question

  1. Aug 9, 2010 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations
    dont think need any equation

    3. The attempt at a solution

    a) i said that if the lightning is simultaneous in rocket frame, then the pilot is in the rockets frame there the rockets frame is the pilots frame therefore the pilot sees it simultaneously. correct?

    b) not sure how to approach it. help
    edit: think i know here goes:
    i used Lorentz transformation, the trees are at equal distance a part(rocket frame. lets say tree1(x1) is to the left then tree2(x2) is to the right.

    i let both t1 wrt tree1 and t2 wrt tree2 be the same b/c t1=t2 because happens at the same time for rocket. then transforming i get t'1=t'2. there student at rest sees as a simultaneous event.
    Last edited: Aug 9, 2010
  2. jcsd
  3. Aug 9, 2010 #2
    would be great if someone can answer this b/c i got finals tomorrow morning.

    BTW not cramming.
  4. Aug 9, 2010 #3
    I think your answer for part B is correct, and we didn't cover relativity in nearly enough detail in my physics class but my intuition is telling me that for (a) the rocket pilot experiences the first lightning strike to be at the right, because in the moment that it occurs, the rocket itself is moving towards the right, hence light from the right tree will reach him first. This is purely based on my speculation, but if you conclude that it's simultaneous to the rocket, the equation implies that its speed in either direction must be 0, which it is not.
  5. Aug 9, 2010 #4


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    [STRIKE]Nope. Think about what happens between the time that lightning actually hits the tree and the time that the pilot sees that happening.[/STRIKE]
    ooooops I totally messed up that one. Yes, the pilot sees the two strikes simultaneously. Think about this, though: what if the two lightning strikes were simultaneous in the frame of the trees/ground/person instead? Make sure you know how you would answer this question in that case.
    No, you didn't actually use the Lorentz transformation anywhere in there. I'm not sure you have to, since this seems to be a conceptual problem, not a mathematical one (and the Lorentz transformation is pure math).

    Do you know how to draw a spacetime diagram? If so, do it. It's an incredibly handy tool for figuring out these kinds of problems. If not, what do you know that might be relevant to this problem?
    Last edited: Aug 9, 2010
  6. Aug 9, 2010 #5
    thanks for reminding me man going to do it right now!

    is theJorge551 correct?
  7. Aug 9, 2010 #6
    what do you mean by""what do you know that might be relevant to this problem? "" im i missing something i should know?
  8. Aug 9, 2010 #7


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    I mean that I am asking you what you know that might be relevant to the problem. Why, do you think you were missing something?

    By the way, note my edit to my previous post.
  9. Aug 9, 2010 #8


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    You get to figure that out :wink:
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