1. The problem statement, all variables and given/known data After being produced in a collision between elementary particles, a positive pion must travel down a 1.90 km long tube to reach an experimental area. A positive pion has an average lifetime of to = 2.60*10^(-8)s; the pion we are considering has this lifetime. How fast must the pion travel if it is not to decay before it reaches the end of the tube? (I put "basic" in the title because it is a chapter in my first year physics program that introduces relativity) 2. Relevant equations L = Lo*(1 - u^2/c^2)^(1/2) or maybe Δt = Δto/(1 - u^2/c^2)^(1/2) where L = 1900m, and Lo = ? (the length of the tube relative to the pion). Δto = 2.60*10^(-8)s, and Δt = ? 3. The attempt at a solution I don't even know where to start because these formulas require more information. Is it even possible to do this question with the information given? If so, can someone help please?