利用毛细管测定油液粘度，已知毛细管直径d=4.0mm，长度L=0.5m，流量Q=25px3/s时，测压管落差h=375px。管中作层流动，油液的运动粘度为（    ）。[img=199x166]17a3dcb618978b7.png[/img]

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" />

米糠油在管中作层流流动,若流量不变,管径不变,管长增加一倍,则摩擦阻力损失为原来的()倍;米糠油在管中作层流流动,若流量不变,管长不变,管径增加一倍,则摩擦阻力损失为原来的()倍。

米糠油在管中作层流流动，若流量增大一倍，管径、管长不变，则摩擦阻力损失为原来的（ ）倍。 A: 2 B: 4 C: 6 D: 8

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" />