一个横放着的圆柱形水桶，桶内放有半桶水。设桶的底半经为
，水的密度为
，则桶的一个端面上所受的压力为
（ ）
，水的密度为，则桶的一个端面上所受的压力为 （ ）
举一反三
- 下列方程为伯努利方程的是（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/0622f56257874ab19e680d587fd8a4fc.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/5ce3fc785b724e3da7d07b8d6a0ecaf3.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/ab3de1c35e9e419fa301a33bddd5ee0c.png">+<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/2c226f2daecf40448b08c3b26a4db60e.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/88be95dd74814341a1894f32f073b9ec.png"><img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/00fbcbc7c3574f94934fa3adc8843ccf.png">
- 直线<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/64709df03a7b45ebbc6d752183b8f22e.png" />与直线<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/5ca5aa44859c42ddaa3207626d2b9537.png" />的公垂线方程为（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/a4c463fa2c3f49df9d7f2bb2e9fc4030.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/627b64a33e944efcba416aea0f40dc76.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/966e8a14e6754060b800dff88721784a.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/f8f41491de204a9eb3fb306208c3b08a.png" />
- 开环系统频率特性<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/d87c0f560f1542028a3602b52456fae0.png" />，当<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/c0f50539680f40a784c2a0d803f0f5d7.png" />时，其频率特性相角<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/ff41a81bec7c421c8178de199c438e05.png" />（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/589b5e2ab46b459882a2824ff9567c36.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/370b677492de485ca61114324b5d00fe.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/95723a2a938f4944a98b18d89f607986.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/c08161009369424f9a3510d7c77d9943.png" />
- 以下哪种图形表示选择结构（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/00e6d9ad2328497da022b3b20603d7f8.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/c6055ccfaafa4eafa3451f45a78535ae.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/b9cd7369284644b29d3499a3025d9cb3.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/8129afad6fcf46cb8c2d79c7e744809e.png">
- 以下哪个公式是周期性功率信号的功率谱密度公式（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/fdca133567634aba8563a0e8202973e7.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/2d25894142c54b0a9841766e40f81a38.png"><img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/a1501c85213b49ca868ac8a509ce450a.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/faae4b3158d64835ac9ab19ca3623915.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/380fffd8c90340a6857c7bdb95721206.png">