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## Homework Statement

Spaceship #1 moves with a velocity of .2c in the positive x direction of reference frame S. Spaceship #2, moving in the same direction with a speed of .6c is 3 x 10^9 m behind. At what times in reference frames S, and in the reference frame of ship #1, will 2 catch up with 1.

## Homework Equations

## The Attempt at a Solution

vrelevative = .6c-.2c / (1-.6(.2)) = .455c

Then, 10 light seconds / .455c =

**22.0s**

Or...is it done classically .6-.2 = .4, making it

**25s**?

For the second part, is it done like so?

beta = 1/(sqrt (1-.2)) = 1.02

Then t = 22/1.02 =

**21.6s**or if it was 25s, 25/1.02 =

**24.5s**

Can someone explain to me which of these two (if either) are correct? I am not sure if it is done classically or with relativity, so can you explain why it is either.

Thank you very much.