以下四个图所示的力三角形，哪一个图表示力矢R是F1和F2两力矢的合力矢量 （ ）
A:
B:
C:
D:
A:
B:
C:
D:
举一反三
- 以下哪个家具是衣架。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/02285e456e2b4861a7f6319515f836c4.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/19a30f3b6d6846ceab656f4ea0e7eb9d.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/e14dbac89fea4066a9ae7bbd6d1dc080.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/612475075e2d434aac0d404ce94395ea.png" />
- 设二极管的端电压为U，则二极管的电流方程为（ ） 。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/8fc1bd7f467e423a9abedfbcf36b63bf.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/96c0065cd93f445abe2243c79b5a11f5.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/e7babcc7dd7c478bbabd8438754ba07b.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/dc06cb808c2a4d20b75fa70ba39feefe.png">
- 给定下述系统的差分方程，则__是非因果系统。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/df1ece1947ea4ec394f9801bb6a8623e.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/4963ffe14fd64ba983b60ad14bd498e2.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/3c6bc338aedb4d04baa637de5d7d9506.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/53dbdd529a5443188250b588e1de8d36.png">
- 系统用差分方程描述如下，x(n)和y(n)分别表示系统输入和输出，则____是非线性系统。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/badc151a5233411b811be09f97702c35.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/def3a29458ab40a787b81bb9f6656d24.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/8323ed0bbbb04ca6a10de2be706bbf3f.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/525c5c85f7ff4ab690f3bade6212d4e6.png">
- 已知图(a)所示梁中点C的挠度为<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/0d6b1c896e51418abc153835c4dd12ed.png"/>（a≥b），则图(b)所示梁中点C的挠度（）。<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/93731d611eba4bc7866c22a14d88acaa.png"/> A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/d68df831261a4f928840f7b55b186e91.png"/> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/cb1390433f4645f2859aed63118634ba.png"/> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/33e997fd31d24eff855f9776e960dd44.png"/> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/185621b86258475ca17377d734005d5e.png"/>