[SOLVED] Displacement and 1-D Kinematics 1. The problem statement, all variables and given/known data A runner runs 15 km, in a straight line, in 20 min and then takes 45 min to walk back to the beginning. Find the average velocity for the whole trip. 2. Relevant equations Vav= (Xf-Xi) / (tf-ti) 3. The attempt at a solution Wouldn't the displacement be 0? If so; what is the average velocity of the whole trip? It couldn't be 0. It would be 0. Silly me.