题目

Jerry Green went to spend a year at the South Pole Station (南极站)as the only doctor in 1998 when she 47. While working at the station that March. she discovered that there was a hard lump (肿块) in her stomach. She knew it was cancer, but she wasn't able to go to a doctor for help. She couldn't leave the station for the next seven until the snow thawed. Dr. Green didn't wait for the death. But decided to fight against the cancer. She tried to about the lump to a hospital in the United States. The doctors said it was cancer. Without the proper wouldn't live for long. Soon a USA airplane 2012年中华龙舟大赛总决赛12月16日在佛山南海区丹灶镇仙湖结束．在当天的决赛中，广东顺德队获得男子总成绩第一名．如图为广东顺德队在比赛中的情景．请根据此情景提出一个物理问题并说明相应的物理知识．物理问题：运动员向后划水，船为什么前进运动员向后划水，船为什么前进物理知识：力的作用是相互的力的作用是相互的．