公式 We differentiate the ideal-gas state equation 式 公式 25. We eliminate dT from the last two equations to get(排除因素得到) 公式 22. We fist examine the path that the motorcycle follows. Taking the air resistance into account differential 公式 Where P is the relative pressure We must first find the speed vl of water at our source: (*3J) 式公式 We differentiate the ideal-gas state equation 公式 Getting 公式 25．We eliminate dT from the last two equations to get （排除因素得到） 公式 22．We fist examine the path that the motorcycle follows. Taking the air resistance into account, we get two differential equations 公式 Where P is the relative pressure. We must first find the speed v1 of water at our source: （找初值） 公式