# Two events in spacetime

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1. May 12, 2013

### ZanyCat

The question...

Two events are observed in a frame of reference S to occur at the same space point, with the second event occurring after a time of 1.70s. In a second frame S' moving relative to S, the second event is observed to occur after a time of 2.25 s.
What is the difference Δx between the positions of the two events as measured in S'?

I know that you guys like people to post their attempt at a solution, but I am legitimately lost and don't even know where to start :(
All I've managed to work out is that for S', event 2 occured $$6.75*10^8$$m away.

Help would be much appreciated.

2. May 12, 2013

### voko

You could start by writing down the relevant equations.

3. May 12, 2013

### ZanyCat

That's the problem, I don't know which equations I need. Do I need time dilation? Do I need to consider length contraction? Do I need to use a Lorentz transformation on the coordinates of something? Do I need to get a Lorentz transformation of a velocity?

I am completely lost with this question in every sense of the word.

4. May 12, 2013

### voko

The problem is obviously talking about time between two events in one frame and in another frame. What equation is relevant there? What can you determine from it?