1. The problem statement, all variables and given/known data Particle track detectors are used to measure the speed of particles if the lifetime of the particle is known. Particle X has a lifetime of 256.2 ps. These particles are created in an experiment inside the detector by a given reaction. The particles leave 21.8 cm long tracks on average before they decay into other particles not observable by the detector. What is the average speed of the particles in terms of the speed of light? 2. Relevant equations Lorentz Transformation equations.. 3. The attempt at a solution The particle's life time is given in the moving reference frame and the track distance is given in the reference frame...so I need to convert either value to the other frame and then the velocity is just the distance traveled divided by the lifetime but how do I transform from either reference frame with the given information? It seems like there is not enough information. Help?