Lorentz Tranformtaions?

1. Sep 12, 2008

Quelsita

Ok, I think for this problem you have to use the Lorentz transformations, but I'm not sure how to consider the velocity.

Question:
At 9 hrs 0min 0sec an aircraft touches down in NY. At 9hrs 0min 0.01sec an aircraft touches down in San Francisco. The (straight) distance between the two is 3.8x10^3km.
a) show that any signal that thepilot of the first aircraft sends after the instant of touchdown will reach the second pilot after his own touchdown.

So, for this x=3.8x10^3km, deltat =0.01sec, but if the aircrafts are stationary, what is the velocity? If it is a singnal, is this just c?

2. Sep 12, 2008

gabbagabbahey

Well, this one looks fairly easy...what is the expression for the average speed $$v_{ave}$$of any signal that travels a distance $${\Delta}x$$ in a time $${\Delta}t$$? If you plug in the distance above along with your $${\Delta}t$$ how fast would the signal have to be? Is it greater or less than c?