在图示系统中， A 点的虚位移大小 d r A 与 C 点的虚位移大小 d r C 的比值 d r A : d r C = _ _________ 。http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/5ad74944a4c24ebc8460d18d9b217716.png
举一反三
- 机构在图示瞬时有，若A点的虚位移为drA，则B点的虚位移的大小drB=____________________，OC杆中点D的虚位移的大小drC=_________________________。http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/78a1ce1550834117b5fb6d4e762ea8d8.png
- 质点作半径为R的变速圆周运动时的加速度大小为（v表示任一时刻质点的速率）( ) A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/566625ddf2c44d81babb2fdd6c1215b2.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/bceb93f381844a3988a0291fea01e102.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/e43ab8d2b7b4422a9088f99e594718cb.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/b1a89995aed242d9b12b93495a7ebdae.png" />
- 两根长度相同的细导线分别多层密绕在半径为R 和r 的两个长直圆筒上形成两个螺线管，两个螺线管的长度相同，R ＝2r，螺线管通过的电流相同为I，螺线管中的磁感强度大小BR 、Br满足( ) A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/c47161e2c0c441e0b5f1e5ec05cfa1a4.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/9389bf043d634884bce774bd44b187ac.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/5cfb777495e44eb297a019eb3eac101d.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/670c7cb2a32d4624b65a86f6466371b3.png" />
- 在图示系统中，A点的虚位移大小drA与C点的虚位移大小drC的比值drA:drC...8460d18d9b217716.png
- 图示交变应力的循环特征r、平均应力σm、应力幅度σα分别为（ ）。http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/ee44ea63da7c42e4ae1a41e3e6625e6e.png