建模示例四：火箭发射问题
1、怎么用火箭发射人造卫星?
(1)卫星能在轨道上运动的最低速度
假设
(i) 卫星轨道为过地球中心的平面圆,卫星在此轨道上作匀速圆周运动.
(ii)地球是固定于空间中的均匀球体, 其它星球对卫星的引力忽略不计.
分析:
根据牛顿第三定律，地球对卫星的引力为:
在地面有:
得: k=gR2
R为地球半径，约为6400公里
故引力:
卫星所受到的引力也就是它作匀速圆周运动的向心力, 故又有:
从而:
构造数学模型,以说明为什么不能用一级火箭而必须用多级火箭来发射人造卫星? 为什么一般都采用三级火箭系统?
2023-08-12 10:32:26
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Delphi 对JSON操作示例 + superobject1.25 下载
2023-08-11 20:50:47
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Main features
Native multi-architecture design (32/64 bit).
Platform independent, currently are supported Windows (from NT 4.0 up to Windows 8), Linux, BSD, Oracle Solaris 11 and Mac OSX.
Multi CPU support : Intel and AMD i386/x86_64, ARM, Sun Sparc, Mips.
Fully scalable, starting from blade servers down to Raspberry PI board.
No dependence on any third-party libraries, no installation needed, zero configuration.
Three different native thread models for performance optimization: Win32 threads/ Posix threads / Solaris 11 threads.
Two data transfer models: classic synchronous and asynchronous.
Two data flow models: polling and unsolicited (PLC transfers data when it wants to).
Two specialized ports : Settimino and Moka7 allow you to communicate with S7 PLC with Arduino or Android phones.
2023-08-11 14:55:24
4.07MB
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主要介绍了Java对XML文件增删改查操作,结合完整实例形式分析了java针对xml格式数据的常见读写、增删改查等操作技巧,需要的朋友可以参考下
2023-08-05 13:44:42
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