1. Sep 8, 2011

### helios.jones

I am a noob! Forgive me if it sounds too stupid!

Let me say, I am in CERN right now at the LHC.
I fire a proton at 0.9c in one direction. While this happens, I also fire another proton at 0.5c in the opposite direction. Both the measurements were done considering the lab as a reference frame.

The problem is, what's the speed(or velocity) of either proton relative to one another??

2. Sep 8, 2011

### Pengwuino

It will be given by $v' = {{v_1 + v_2}\over{1+{{v_1v_2}\over{c^2}}}}$