1. The problem statement, all variables and given/known data Ted and Mary are playing a game of catch in frame S', which is moving at 0.600c with respect to frame S, while Jim, at rest in frame S, watches the action. Ted throws the ball to Mary at 0.800c (according to Ted) and their separation (measured in S') is 1.8*1012m. According to Jim, how far apart are Ted and Mary, and how fast is the ball moving? According to Jim, how long does it take the ball to reach Mary? 3. The attempt at a solution In this case, I cant use length contraction to calculate the relative length by Jim. But, it is wrong for time dilation. I got a wrong answer when I calculate the relative time taken by Jim by using t'=[tex]\gamma[/tex]t. Another approach is to use Lorentz velocity transformation to calculate the relative velocity. But I don understand why I can apply time dilation in this case because it works well for other questions.