1. The problem statement, all variables and given/known data The rod AB oriented parallel to the x' axis of the reference frame K' moves in this frame with a velocity v' along it's y' axis. In its turn, the frame K' moves with a velocity V relative to the frame K as shown in Figure. Find the angle (theta) between the rod and the x-axis in the frame K. 2. Relevant equations Lorentz Transformation: x' = (x-Vt)/(1-(V/c)2)1/2; y = y' (Doubtful in this case) vx' = vx - V/(1-vxV/c2); vy' = vy (1-(V/c)2)1/2/(1-vxV/c2). 3. The attempt at a solution As far as I know that the rod AB in frame K should not be tilted at all, I mean it must remain horizontal if x and x' axis of K and K' frames coincide, or am I wrong? So, my only problem is that - "Is it possible for rod to be tilted in frame K?"