1. The problem statement, all variables and given/known data In a race, a 54 kg athlete runs from rest to a speed of 11m/s on a flat surface. The athlete's body has an efficiency of 85% during the run. How much input energy did the athlete provide? 2. Relevant equations efficiency = E out/E in x 100% 3. The attempt at a solution I know E in = E out/efficiency and efficiency = 85%, m = 54 kg, vi = 0, vf = 11 m/s but how can I find E out? Eg = mgh ? There's no height though...?