I could use the equation (ΔT/Δt)=√(1-(v/c)^2) but I'm still a little unsure on the reference frames. Is the first reference from from the pion and the second from a stationary observer?
How fast must a pion be moving, on average, to travel 9.0 m before it decays? The average lifetime, at rest, is 2.60 ✕ 10-8 s. (Answer in terms of c)
I'm not exactly sure what equations I have to use but I believe it relates to time dilation.
I originally didn't realize it was a time...