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Homework Help: This doesn't seem to be working? Relativity

  1. Jan 20, 2012 #1
    Evaluate the derivative of [tex]\vec{F} = \frac {d} {dt} \frac {m \vec{v}} {\sqrt{1 - v^2/c^2}}[/tex] to find the acceleration [tex] a = \frac {dv}{dt} [/tex] of the particle.

    So, basically, I just tried to use the quotient rule and treat m, and the whole bottom of the fraction as constants. I didn't end up getting the right answer and I can't figure out why. As reference, here are two answers I've tried, both wrong:

    [tex]\frac {F}{m} \sqrt {1 - \frac {v^2}{c^2}}[/tex]
    [tex]\frac {F}{m} (1 + \frac {v^2}{3c^2})[/tex]
    Last edited: Jan 20, 2012
  2. jcsd
  3. Jan 20, 2012 #2


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    How can you treat v2 as a constant?
  4. Jan 20, 2012 #3
    Remember the fact that:

    [tex]\frac{dv}{dt}=\frac{\vec{a}\cdot \vec{v}}{v}[/tex]
    Last edited: Jan 20, 2012
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