幂级数
It was a common ride at major amusement parks until the late 1990s, when the classic freefall rides began being replaced with larger, higher-capacity Drop Tower alternatives. Since then, Freefalls have been disappearing from midways, to be replaced by the newer-technology rides such as the Intamin Giant Drop (2nd generation), Gyro Drop (3rd generation), and the S&amp;S Power series of compressed-air tower rides.