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<HTML><HEAD><TITLE>new</TITLE><META content="text/html; charset=gb2312" http-equiv=Content-Type><LINK href="text.css" rel=stylesheet type=text/css><META content="Microsoft FrontPage 4.0" name=GENERATOR></HEAD><body leftmargin="15"><table border="0" cellpadding="0" cellspacing="0" width="560"> <tr> <td><b>例1</b> 计算双摆的广义力，已知摆长各为l<font size="1">1</font>、l<font size="1">2</font>，重量各为W<font size="1">1</font>、W<font size="1">2</font>，力P。（2自由度）</td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="50%"><b>解1</b>：<font color="#800000">（解析法）</font>建立坐标系如图。选φ<font size="1">1</font>、φ<font size="1">2</font>为广义坐标。</td> <td width="50%" rowspan="5"><img border="0" src="pic2/3072_183.GIF" width="250" height="183"></td> </tr> <tr> <td width="50%">各力在坐标轴上的投影为</td> </tr> <tr> <td width="50%"><img border="0" src="pic2/3072_184.GIF" width="199" height="25"></td> </tr> <tr> <td width="50%">各力作用点坐标为</td> </tr> <tr> <td width="50%"><img border="0" src="pic2/3072_185.GIF" width="267" height="69"></td> </tr> </table> </td> </tr> <tr> <td>代入广义力公式（过程略，你可以再详细些），得</td> </tr> <tr> <td><img border="0" src="pic2/3072_186.GIF" width="455" height="109"></td> </tr> <tr> <td><b>解2</b>：<font color="#800000">（几何法）</font>选φ<font size="1">1</font>、φ<font size="1">2</font>为广义坐标，对应虚位移为δ<font size="1">φ1</font>、δ<font size="1">φ2</font>。</td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="50%">①先令δ<font size="1">φ1</font>≠0、δ<font size="1">φ2</font>＝0，如图（a）。<br> 所有力在此虚位移上的虚功为：</td> <td width="50%" rowspan="4"><img border="0" src="pic2/3072_187.GIF" width="236" height="192"></td> </tr> <tr> <td width="50%"><img border="0" src="pic2/3072_188.GIF" width="362" height="121"></td> </tr> <tr> <td width="50%">所以，对应φ<font size="1">1</font>的广义力为</td> </tr> <tr> <td width="50%"><img border="0" src="pic2/3072_189.GIF" width="305" height="49"></td> </tr> </table> </td> </tr> <tr> <td>②再令δ<font size="1">φ2</font>≠0、δ<font size="1">φ1</font>＝0，如图（b）。</td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="50%">所有力在此虚位移上的虚功为：</td> <td width="50%" rowspan="5"> <p align="center"><img border="0" src="pic2/3072_190.GIF" width="242" height="192"></td> </tr> <tr> <td width="50%"><img border="0" src="pic2/3072_191.GIF" width="269" height="121"></td> </tr> <tr> <td width="50%">所以，对应φ<font size="1">2</font>的广义力为</td> </tr> <tr> <td width="50%"></td> </tr> <tr> <td width="50%"><img border="0" src="pic2/3072_192.GIF" width="267" height="49"></td> </tr> </table> </td> </tr> <tr> <td></td> </tr> <tr> <td> <p align="center"> <a href="3071_5.htm"><font color="#FF6666">[ 上一节 ]</font></a> <a href="3072_1.htm">↑上一页↑</a> <a href="3072_2.htm"><font color="#00CC00">[ 下一节 ]</font></a> </td> </tr> </table> </BODY></HTML> ⌨️ 快捷键说明
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