设有一质点从A点作曲线运动到B点，如图1所示，A点和B点的位置矢量分别是 <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/0d76b5d4340c46fe8a8c4b8c35e04bde.png" />，则它们的大小之差<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/5ef37da7a8ec41729fdb08c5e0470007.png" />和它们的矢量差的大小<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/74f7e5aeb58746f990b78a02b130b693.png" />分别是（）<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/db95db190cf342bf902e99c4d8f76e6a.png" /> A: 2m，0 B: -1m，1m C: 0，0 D: 2m，2m E: 1m，1m F: 0，2m

图示曲柄连杆机构，已知曲柄OA长L，重量不计，连杆AB长2L，重P，受矩为M的力偶和水平力Ｆ的作用，在图示位置平衡。若用虚位移原理求解，则必要的虚位移之间的关系为___________，力F的大小为_____________________。<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/be06434307bd424abfc4ebfe02661f7a.png" /> A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/b8e7b964d1c84aeca7b22ddef4de87a2.png" />;<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/a584946cde17410c945d6611ff2113b5.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/1aaef24e28ee477ab25dae0a400bf23f.png" />;<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/f3b395453e1d48bdadff2e37dfbbb626.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/be37912822f0451bb15639b7fa0589f1.png" />;<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/6d1112b5c1b4446b93578138388ed79f.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/89b7bcef6b51410cb624a654747d56ee.png" />;<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/0e2b78f437914a1eb8327d13185eaedf.png" />

理想情况下有一单摆,在小球摆动过程中,小球的动量____;小球与地球组成的系统机械能____;小球对细绳悬点的角动量____(不计空气阻力).(填守恒或不守恒)

Which one is Homer’s epic? A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/60a09e42c1cb4c988adcf2fa43a2170c.png"> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/148a547a82cd4f5482de272b09415b7f.png"> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/bc77b52b6ae747fda43ef56a09994b9f.png"> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/9a18e23e6d9a453ea18eaabd88d99376.png">

What are the “Four Great Tragedies” of Shakespeare? A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/bf2842136acc4afba0ab8f98320c7d00.png"/> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/ac6493ebe0b44370ac61898fa86c032b.png"/> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/b34e70254de6499eb4641abf0415463b.png"/> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/5a8ed85351f948a393c0aca57418e72a.png"/>