?? 30831.htm
字號:
<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> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="50%">例2 求例1中系統(tǒng)振動的固有頻率。</td> <td width="50%" rowspan="4"> <p align="center"><img border="0" src="pic2/30821.34.gif" width="277" height="193"></td> </tr> <tr> <td width="50%">解1：（通過建振動方程求）</td> </tr> <tr> <td width="50%"> <table border="0" cellpadding="0" cellspacing="0" width="290"> <tr> <td width="170">例1已求得標(biāo)準(zhǔn)振動方程</td> <td width="116"><img border="0" src="pic2/30821.35.gif" width="116" height="47"></td> </tr> <tr> <td width="170">則系統(tǒng)振動的固有頻率為</td> <td width="116"><img border="0" src="pic2/30821.36.gif" width="115" height="59"></td> </tr> </table> </td> </tr> <tr> <td width="50%">解2：（能量法）</td> </tr> </table> </td> </tr> <tr> <td>設(shè)重物自初始上升s，各物體速度如圖。系統(tǒng)在任一位置的動能：</td> </tr> <tr> <td><img border="0" src="pic2/30821.37.gif" width="496" height="47"></td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0"> <tr> <td>設(shè)系統(tǒng)在靜平衡位置時，彈簧伸長量為 s0 。令 </td> <td><img border="0" src="pic2/30821.38.gif" width="195" height="28"></td> </tr> </table> </td> </tr> <tr> <td>則：</td> </tr> <tr> <td><img border="0" src="pic2/30821.39.gif" width="184" height="47"></td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0"> <tr> <td>而速度振幅：</td> <td><img border="0" src="pic2/30821.40.gif" width="91" height="28"></td> </tr> <tr> <td>則系統(tǒng)振動時最大動能：</td> <td><img border="0" src="pic2/30821.41.gif" width="152" height="47"></td> </tr> </table> </td> </tr> <tr> <td></td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="50%">設(shè)系統(tǒng)靜平衡位置為0勢能點(diǎn)，此時彈簧伸長量為s0，系統(tǒng)在任一位置的勢能為：</td> <td width="50%" rowspan="2"> <p align="center"><img border="0" src="pic2/30821.42.gif" width="277" height="193"></td> </tr> <tr> <td width="50%"><img border="0" src="pic2/30821.43.gif" width="266" height="117"></td> </tr> </table> </td> </tr> <tr> <td><img border="0" src="pic2/30821.44.gif" width="405" height="47"></td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="50%">在靜平衡位置，給系統(tǒng)虛位移，由虛位移原理：</td> <td width="50%" rowspan="5"> <p align="center"><img border="0" src="pic2/30821.45.gif" width="260" height="197"></td> </tr> <tr> <td width="50%"><img border="0" src="pic2/30821.46.gif" width="272" height="27"></td> </tr> <tr> <td width="50%"><img border="0" src="pic2/30821.47.gif" width="249" height="27"></td> </tr> <tr> <td width="50%"><img border="0" src="pic2/30821.48.gif" width="225" height="27"></td> </tr> <tr> <td width="50%"> <table border="0" cellpadding="0" cellspacing="0"> <tr> <td>則系統(tǒng)勢能： </td> <td><img border="0" src="pic2/30821.49.gif" width="69" height="44"></td> </tr> <tr> <td>而位移振幅：</td> <td><img border="0" src="pic2/30821.50.gif" width="70" height="28"></td> </tr> </table> </td> </tr> </table> </td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0"> <tr> <td>則系統(tǒng)最大勢能： </td> <td><img border="0" src="pic2/30821.51.gif" width="89" height="44"></td> </tr> </table> </td> </tr> <tr> <td>系統(tǒng)為單自由度自由振動，由能量法：</td> </tr> <tr> <td> <p align="center"><img border="0" src="pic2/30821.52.gif" width="80" height="25"></td> </tr> <tr> <td>即：</td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0"> <tr> <td><img border="0" src="pic2/30821.53.gif" width="162" height="47"></td> <td> </td> <td><img border="0" src="pic2/30821.54.gif" width="195" height="60"></td> </tr> </table> </td> </tr> <tr> <td> <table border="1" cellpadding="0" cellspacing="0" bordercolor="#008080"> <tr> <td> <table border="0" cellpadding="0" cellspacing="0"> <tr> <td>注：也可由靜力學(xué)平衡方程求出關(guān)系式： </td> <td><img border="0" src="pic2/30821.55.gif" width="140" height="25"></td> </tr> </table> </td> </tr> </table> </td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="50%">在靜平衡位置，考慮滾子、滑輪、重物的平衡：</td> <td width="50%" rowspan="8"> <p align="center"><img border="0" src="pic2/30821.56.gif" width="260" height="197"></td> </tr> <tr> <td width="50%"><img border="0" src="pic2/30821.57.gif" width="90" height="26"></td> </tr> <tr> <td width="50%"><img border="0" src="pic2/30821.58.gif" width="217" height="32"></td> </tr> <tr> <td width="50%"> </td> </tr> <tr> <td width="50%"> </td> </tr> <tr> <td width="50%"> </td> </tr> <tr> <td width="50%"> </td> </tr> <tr> <td width="50%"> </td> </tr> </table> </td> </tr> <tr> <td></td> </tr> <tr> <td> <p align="center"> <a href="3082.htm"><font color="#FF6666">[ 上一節(jié) ]</font></a> <a href="3083.htm">↑上一頁↑</a> <a href="3084.htm"><font color="#00CC00">[ 下一節(jié) ]</font></a> </td> </tr> </table> </BODY></HTML> ?? 快捷鍵說明
復(fù)制代碼
Ctrl + C
搜索代碼
Ctrl + F
全屏模式
F11
切換主題
Ctrl + Shift + D
顯示快捷鍵
?
增大字號
Ctrl + =
減小字號
Ctrl + -