2024·山东·模拟预测
解题方法
1 . 如图①,将
个完全一样质量均匀长为
的长方体条状积木,一个叠一个,从桌子边缘往外延伸,最多能伸出桌缘多远而不掉下桌面呢?这就是著名的“里拉斜塔问题”.
![](https://img.xkw.com/dksih/QBM/editorImg/2024/3/23/bc879c7d-8f43-4e6c-b6d8-ddd10ad2a335.png?resizew=507)
解决方案如下:如图②,若
,则当积木与桌缘垂直且积木重心
恰与桌缘齐平时,其伸出桌外部分最长为
,如图③,若
,欲使整体伸出桌缘最远,在保证所有积木最长棱与桌缘垂直的同时,可先将上面积木的重心与最下方的积木伸出桌外的最远端齐平,然后设最下方积木伸出桌外的长度为
,将最下方积木看成一个杠杆,将桌缘看成支点,由杠杆平衡原理可知,若积木恰好不掉下桌面,则上面积木的重力
乘以力臂
,等于最下方积木的重力
乘以力臂
,得出方程
,求出
.所以当叠放两个积木时,伸出桌外最远为
,此时将两个积木看成整体,其重心
恰与桌缘齐平.如图④,使前两块积木的中心
与下方的第三块积木伸出桌外的最远端齐平,便可求出
时积木伸出桌外的最远距离.依此方法,可求出4个、5个直至
个积木堆叠伸出桌外的最远距离.(参考数据:
,
为自然常数)
(1)分别求出
和
时,积木伸出桌外的最远距离.(用
表示);
(2)证明:当
时,积木伸出桌外最远超过
;
(3)证明:当
时,积木伸出桌外最远不超过
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c88d9142df6ba8e43c1a93bd04a1362.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/3/23/bc879c7d-8f43-4e6c-b6d8-ddd10ad2a335.png?resizew=507)
解决方案如下:如图②,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c87b351f16728b0023fd63678f8103c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/23f919bd3dde10dbbc076f7ec5149699.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b00c12002fe4b07e3f91c7ae5c9192dd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cc2d3df37e73a8abea815f37dbb3fff5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc11468f07d42dda1d7d51107aab02fe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/18b4ed74387268c43450135937805101.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7050b91eacc62f73d872eeb628f3565c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2926c82d9ad9f5ba647c83fa3024f323.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c4f6f74444b2b7947fc6e35c8d62322.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c4f6f74444b2b7947fc6e35c8d62322.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be604061cf1591f7069472269d4c9719.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0af3a30b2f1dbc2fa12eb6759eee69d0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/041a7c8fc017f596542c5e6ec7d1c40b.png)
(1)分别求出
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be604061cf1591f7069472269d4c9719.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fac3649308b528fd56545ba102dc42d5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c88d9142df6ba8e43c1a93bd04a1362.png)
(2)证明:当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca71b6d6fd74f098d1e78161820dd3b6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0d916a406adac9fa4dcfbad152547ac9.png)
(3)证明:当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/30589b25ca71883ec4a5d1824c243bad.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81731a804207d04115c15a16f3a27011.png)
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名校
2 .
技术的价值和意义在自动驾驶、物联网等领域得到极大的体现.其数学原理之一是香农公式:
,其中:
(单位:
)是信道容量或者叫信道支持的最大速度,
单位;
)是信道的带宽,
单位:
)是平均信号功率,
(单位:
)是平均噪声功率,
叫做信噪比.
(1)根据香农公式,如果不改变带宽
,那么将信噪比
从1023提升到多少时,信道容量
能提升![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1078cd967972b58c8eb2783d8b7a41f5.png)
(2)已知信号功率
,证明:
;
(3)现有3个并行的信道
,它们的信号功率分别为
,这3个信道上已经有一些相同的噪声或者信号功率.根据(2)中结论,如果再有一小份信号功率,把它分配到哪个信道上能获得最大的信道容量?(只需写出结论)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/47248d88a8876e1177cbd3ba43b11bea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/70215f90c7b8bd048aeab814ffcb1075.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0594324ac79e120d87761d147159f93.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/53801bf39bf5de59f2853caeac6f8784.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/72bc766cbead9ec6fb613abe669b0be2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/14bfbd55ad2a343daee3194b30a4cca2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca586d4c35ce52dec4b545cf13ee0721.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca586d4c35ce52dec4b545cf13ee0721.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/848c6dc59f47173493581489dde138df.png)
(1)根据香农公式,如果不改变带宽
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91edc7e2d4811f5ea6c01284cf00393a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/848c6dc59f47173493581489dde138df.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1078cd967972b58c8eb2783d8b7a41f5.png)
(2)已知信号功率
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7d654dec2ae3a0f1dda3420b354d38b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0116640668a4da68b97f4f7809a95a7.png)
(3)现有3个并行的信道
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/67b0ea548b200fd74a2412d13c00e077.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e717353515a0c6f3423dd25b42509006.png)
您最近一年使用:0次
2023-03-16更新
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266次组卷
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6卷引用:北京市丰台区普通高中2020-2021学年数学合格性调研试卷
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