# Homework Help: 2 objects travelling in seperate dimensions

1. Apr 14, 2010

### nSMITH

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

One object is travelling in the x direction at 0.935c and another is travelling at 0.98c in the z direction. Determine the overall velocity of the second object from the point of view of the first object.

2. Relevant equations

v'x=(vx-v)/(1-vx*(v/c^2))

3. The attempt at a solution

I have no idea where to start

2. Apr 14, 2010

### irycio

Having no idea where to start, you should have checked wikipedia:P
And off you go with a beautiful formula for adding orthogonal velocities in SR. Couple more years and I'll be able to derive it myself \m/. Till then, use google :P

3. Apr 14, 2010

### nSMITH

You think I'd be asking here if I could figure it out from wikipedia/google?

4. Apr 14, 2010

### irycio

My apologies for providing you with a wrong formula.
No apologies, however, for suggesting you to google, because after a couple more minutes... http://www.mathpages.com/home/kmath216/kmath216.htm here you are, the proper formula:
v=Sqrt[1-(1-vx^2)(1-vy^2)]
I'm afraid i dunno where it comes from, but the result seems fine, as it increases both of the velocities, still being less then c, whereas the formula form wikipedia gave the result that was lesser than 0.98c.
No offence :)