Charlie loves the creativity of freestyle skiing and he works to get maximum air out of the half pipe. Guest pro Drew provides some tips on how to crouch and pump to get maximum height. Dr. Heather explains centripetal acceleration, when acceleration changes from horizontal to vertical. Warmer temperatures can make the snow more difficult to ski on because of cohesion and adhesion. Ski jumping began in Norway, and in the 1920's, US skiers started developing flips.