1. The problem statement, all variables and given/known data Two space ships A (90m long) and B (200m long) travel towards each other. The person in ship A observes that it takes 5x10-7s for the tip of ship B to pass his ship. What’s the relative speed of the two ships? How long does a person sitting at the tip of ship B observe for his ship to pass ship A? 3. The attempt at a solution at the moment in class we are on the topic of Lorentz transformations. so i am going to assume that this problem is to be done in that way. i am having a hard time in general setting up any equations to these word problems as this new idea of reference frames is confusing me in terms of writing the equations. so what i got so far is this (with help from my textbook, not really from any understanding of my own): i am going to start by indicating that spaceship A will be the fixed system K, and spaceship B be will be the moving system K'. since i am given Δt i figure that i would have to solve for the apparent velocity of the system u'. u'=dx'/dt', using the lorentz transformation i plug in dρ(x-vt)/dρ(t-vx/c^2) ρ=1/sq.rt.(q-(v/c)^2) and after some algebra i get u'=u-v/1-vx/c^2). the time it takes for person sitting at the tip of ship B observe his ship to pass ship A im going to call Δt'=t2'-t1'. using the lorentz transformation i get ρ(t2-vx2/c^2)-ρ(t1-vx1/c^2) and after some algebra i got ρ[(t2-t1) - (v/c^2)(x2-x1)]. t2-t1=Δt=5 x 10^-7s and x2-x1=90m (i think), and i would think i answered the question, but as i said before i kinda just got it from the textbook if someone could help explain some of this to me.