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Relativity questions

  1. Aug 31, 2004 #1
    A friend gave me these questions to answer.

    "A certain star is 7.0 light years away. How long would it take a spacecraft traveling at .950c to reach that star from Earth, as measured by observers (a ) on earth (b )on the aircraft (c ) what is the distance travled according tio observers on the spacecraft? (d ) what will the spacecraft occupants compute their speed to be from the results of (b ) and (c )?"

    I fear taking the obviouse path, for it may take me to answer which contradicts that which you would get if you applied the lorentz transformations, which I know nothing of. What would be the correct way of going about this question?

    and this was the second question.

    "Derive the general relativist equation of T = To sr (1 - v^2/c^2)"

    I have no idea of how to go solving about this one.
  2. jcsd
  3. Aug 31, 2004 #2
    [tex] v = \frac{d}{t} [/tex]

    [tex] t = \frac{d}{v} [/tex]

    [tex] t = \frac{7.0cy}{0.950c} [/tex]

    [tex] t = 7.4y [/tex]

    [tex] t = t_o \sqrt{1-v^2 / c^2} [/tex]

    [tex] t = (7.4y) \sqrt{1-(0.950c)^2 / c^2} [/tex]

    [tex] t = (7.4y) \sqrt{1-(0.9025c^2 / c^2} [/tex]

    [tex] t = (7.4y) \sqrt{1-(0.9025)} [/tex]

    [tex] t = (7.4y) \sqrt{0.0975} [/tex]

    [tex] t = (7.4y)(0.3122) [/tex]

    [tex] t = 2.3y [/tex]

    [tex] d = d_o \sqrt{1-v^2 / c^2} [/tex]

    [tex] d = (7.0ly) \sqrt{1-(0.950c)^2 / c^2} [/tex]

    [tex] d = (7.0ly) \sqrt{1-(0.9025c^2 / c^2} [/tex]

    [tex] d = (7.0ly) \sqrt{1-(0.9025)} [/tex]

    [tex] d = (7.0ly) \sqrt{0.0975} [/tex]

    [tex] d = (7.0ly)(0.3122) [/tex]

    [tex] t = 2.19ly [/tex]

    [tex] v = \frac{d}{t} [/tex]

    [tex] v = \frac{2.19ly}{2.3y } [/tex]

    [tex] v = 0.950c [/tex]

    Do you get it?
    Last edited: Aug 31, 2004
  4. Aug 31, 2004 #3
    Yes. I do get it.
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