Starts with Kepler three laws, and analyzes the conservational quantity in this kind of motion. 从开普勒三定律出发，分析这类运动中的守恒量。
Throwing rice seedlings with conservational tillage measures can effectively improve ecological environment, increase the 1000-grain weight and rice yield. 免耕抛秧保护性耕作措施能有效改善生态环境，增加水稻千粒重，促进水稻增产。
