杆AB的两端可分别沿水平，铅直滑道运动，已知B端的速度为vB，则图示瞬时B点相对于A点的速度为___________。
A:
B: vBsinq
C:
D: vBcosq
A:
B: vBsinq
C:
D: vBcosq
举一反三
- 船A重P<sub>A</sub>，以速度 <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/1e6a475774084108a4d9ded2c70e6ca1.png" />航行。重P<sub>B</sub>的物体B以相对于船的速度<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/b39c5c7163f846e8bc34287ec16ef1a7.png" />空投到船上，<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/20f0fb6f6dbc40638b69c7a33e96fd41.png" />设与水平面成<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/3651093fa407458596d5b85ce9b1dc5d.png" />角，且与<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/14fe1be64d75470c8843680bac3209a7.png" />在同一铅直平面内。若不计水的阻力，则二者共同的水平速度为____________。<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/9456cc95f694413584344f4bad82d008.png" /> A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/910e6572478f418c97aa55ae3e71eb87.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/eb921b41a733425c811ac7b3848f3afe.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/06d430260f9c402eaf641a0ba96427c5.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/4c6f547166aa4497b9c6e8ff20fb5407.png" />
- 图示单元体应力状态，沿x方向的线应变εx可表示为（ ）。 <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/9fdd7efe625f4047bb61ef38f5aea871.png" /> A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/5da2d36f7ef84cbc8396b1e27b775bf4.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/164a3d85fdb6462696d83d62b92b2435.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/9e37e58e1c12442e8e018c0af637dfdf.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/41fd81417e5f47bea1db35fed7c2c44e.png" />
- 拉普拉斯（Laplace）方程的表达式为（ ）。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/26731bcad75f41389448b29292940653.jpg" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/40e7e55a72ee44f59b45d20c84ebe3a6.jpg" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/c65a79ea4d754174b99f34020d6e1735.jpg" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/139e8d3dc37941549e7b6b1731243172.jpg" />
- 平面一维稳定渗流的压力分布公式为（ ）。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/d08348f3b84f442d87994311dc13686b.jpg" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/2df214c86c5e4103897ba81ce2c6cd98.jpg" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/cc98e4a778cc463c965ac8115e028f86.jpg" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/bc82177c19d44acfa1b365c3d66ed0a4.jpg" />
- 一质点在平面上作一般曲线运动，其瞬时速度为<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/072ecbf2079c40debf10e59602baef5a.png" />，瞬时速率为<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/a7c386a2ed9641fb872fd3798d8a18d6.png" />，某一段时间内的平均速度为<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/fd7b24d84b0c48b29b905c0accbfb682.png" />，平均速率为<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/25c97028c3294855859e6d26731aecd6.png" />，它们之间的关系必定有（ ） A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/28eb779628f849cb9c561087ac27668c.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/332a22fc817749108da3ea994f11c24e.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/9fee0e92ea9344e18d11908ba83a7529.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201812/258f415ef0974549b35f450f710027de.png" />