题目

根据短文内容及首字母提示完成短文，使短文完整、通顺。There is a nature park in the southwest of our city. The government built it to p【1】 the rare animals. The nature p【2】 has been the s【3】 of our city.Yesterday my friends and I visited it. The workers there asked us not to f【4】 animals. Many animals are in d【5】 because people kill them for their meat and fur. Another reason is that people are taking a【6】 their land and making their water d【7】. The s【8】 is becoming very serious.I learnt much yesterday. I think people should s【9】 up m）竖直放置的两块足够长的平行金属板间有匀强电场，其电场强度为E，在该匀强电场中，用丝线悬挂质量为m的带电小球，丝线跟竖直方向成θ角时小球恰好平衡，小球与右侧金属板相距d，如图所示，求： （1）小球带电荷量q是多少？ （2）若剪断丝线，小球碰到金属板需多长时间？