1. The problem statement, all variables and given/known data A pion traveling near the speed of light hits a nucleus and travels an average distance of 3.5fm before interacting. Estimate the time req. for the strong force to interact. 2. Relevant equations 3. The attempt at a solution So are they saying that the pion hits the nucleus travels 3.5fm, then the strong force acts on it? It would be kin. eqs. to solve then right?