1. The problem statement, all variables and given/known data Athletes who compete in downhill skiing try to lose as little energy as possible. A skier starts from rest at the top of a 65 m hill and skis to the bottom as fast as possible. When she arrives at the bottom, she has a speed of 23 m/s. Calculate the skier's efficiency. Explain why the mass of the skier is not required when calculating the efficiency. 2. Relevant equations Eg = mgh 3. The attempt at a solution I don't understand since Eg = mgh, and I'm only given height and velocity. How could I possibly find the skier's efficiency without mass? *Also, another question asks how I could determine power without time. How is this possible when P = E/t?