# Simple Lorentz transformation problem

1. Apr 13, 2010

### brooktrout

1. The problem statement, all variables and given/known data

3. At what speed (measured in units so c = 1) must the train be moving in order for the points(X,T) = (1,1) and (X,T) = (5,2) to be simultaneous in the (X',T') coordinate system?

2. Relevant equations

Disclaimer: I'm not actually in a physics class, I'm in an elementary college math class that's doing a special relativity unit. So I know very little about physics.

I do know we have to use Lorentz Transformations, so that would be:

X= X'/(square root (1-(v^2/c^2) + VT'/(square root (1-(v^2/c^2)
and T = VX'/C^2(square root (1-(v^2/c^2) + T'/square root (1-(v^2/c^2)

3. The attempt at a solution

OK, so here's the thing. I just want to know where to begin; i.e., how to set up my equations. I can do the math once I get there, but I really don't even get what this question is asking...where do I put in the given coordinates, and to which of the given equations? That's all I need to know.

Thank you so much! Hope this followed all forum guidelines, I'm not looking for anybody to do my homework at all, just a little hint about where to start.

2. Apr 13, 2010

### Staff: Mentor

Last edited by a moderator: Apr 25, 2017
3. Apr 13, 2010

### tiny-tim

welcome to pf!

hi brooktrout! fishy welcome to pf!

(have a square-root: √ and try using the X2 tag just above the Reply box )
hint: the 4-vector joining them is (4,1)