图所示电路中，网孔方程为 则R21=（ ）Ω。http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/1dc683a3c9e34636b3a2bb2f2004d31b.png
举一反三
- 敞口容器内装有两层静止液体，上层密度为ρ1，静力学方程为http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/f2015d0ddc2146a5bd4ee7baeb099d7b.png；下层的密度为ρ2，静力学方程为http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/a37b8588d29545eba8c0068fe4189e5b.png。因ρ1＜ρ2，取同一基准面，则C1（）C2。
- 如图，等直径管，考虑损失，A-A断面为过流断面，B-B断面为水平面，试确定1、2、3、4各点的物理量有以下关系（ ）。<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/221f6e4fdefe4fc8a4dccb77b349aa72.jpg" /> A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/ace37017ba8545728a2182f386058ba6.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/70b91bd905944a2b94af05cde3e27218.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/2000acab49234b1b95b2c3ecc59dfd3c.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/3d47348e1e6f46a99ed44f691c648298.png" />
- 在如图所示电路中，网孔2的网孔电流方程应为（ ）。http://image.zhihuishu.com/zhs/onlineexam/ueditor/201804/697a3c5dc73149dea4306270d3ec390e.png
- 在如图所示电路中，网孔2的网孔电流方程应为（）。http://image.zhihuishu.com/zhs/onlineexam/ueditor/201804/697a3c5dc73149dea4306270d3ec390e.png
- 如图9所示，建筑装修中，工人用质量为m的磨石对斜壁进行打磨，当时磨石加竖直向上大小为F的推力时，磨石恰好沿斜壁向上匀速运动，已知磨石与斜壁之间的动摩擦因数为 <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/8f90c371679b495faa8e0712ca86bd45.png" />，则磨石受到的摩擦力是（）<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/a9b96947560c4fb3b2d2878f99c076c1.png" /> A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/8ec695bac8e344da9c2dce17e053d2b7.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/75657b0b2e1f48328d47630c210769d2.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/8ff12bbcf235454885e8e28ee2735858.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201901/f2efc236752b455b87169561201d7b81.png" />