1. The problem statement, all variables and given/known data A runner covers one lap of a circular track 40.0 min diameter in 62.6 s . 2. Relevant equations If she covered the first half-lap in 28.7 s , what were her average velocity for that half-lap? 3. The attempt at a solution Attempt 1: Initial Distance: 0 m Distance of a half-lap: 20π m Initial Time: 0 s Final Time: 28.7 s Displacement = Δx/Δt, where Δx = xf - x0 Displacement = (20π m - 0 m)/28.7 s = 2.19 m/s Attempt 2: By inspection, her total distance is aligned original position, making Δx = 0, thereby making displacement = 0.