1. The problem statement, all variables and given/known data A 70.0 kg skier rides a 2700 m long lift to the top of a mountain. The lift makes an angle of 14.3° with the horizontal. What is the change in the skier's gravitational potential energy? 2. Relevant equations 3. The attempt at a solution mg cos(?) * (h0 - hf) again, not sure why this formula doesnot work.