#### Pengwuino

Gold Member

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[tex]Delta t = t_2 - t_1 = \frac{2}{c}(\frac{{l_2 }}{{\sqrt {1 - \frac{{v^2 }}{{c^2 }}} }} - \frac{{l_1 }}{{1 - \frac{{v^2 }}{{c^2 }}}})[/tex]

I need to show that if the length is contracted along the direction of motion, the result comes out to be 0. My question is, which direction is the direction of motion? I have a feeling its L1....