Abstract: This study focuses on the vertical launch of a water bottle rocket and explores the law of acceleration change during its vertical launch through a combination of theoretical modeling and experimental measurement. Based on variablemass motion, a dynamic model considering factors such as water jet recoil, air resistance, and gravity is established, and the theoretical calculation formula for the vertical launch acceleration of the water bottle rocket is derived. Meanwhile, an acceleration sensor is used to measure relevant data during the launch process. By comparing theoretical and experimental results, the main factors affecting the vertical launch acceleration of the water bottle rocket are analyzed, including initial water filling volume, initial air pressure inside the bottle, bottle volume, and nozzle crosssectional area. The research results show that the theory is highly consistent with the experiment under different pressures. The achievements of this study provide a theoretical and experimental basis for optimizing the launch performance of water bottle rockets.

Key words: water bottle rocket, vertical launch, acceleration