?? 3051_3.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"><center><b><br>3 動能定理</b></center> <table border="0" cellpadding="0" cellspacing="0" width="560"> <tr> <td width="20"><b><font color="#0000FF">一、</font></b></td> <td width="540"><b><font color="#0000FF">質點的動能定理</font></b></td> </tr> <tr> <td width="20"></td> <td width="540"> <table border="0" cellpadding="0" cellspacing="0"> <tr> <td><img border="0" src="pic/3051_380.GIF" width="63" height="27"></td> <td><img border="0" src="pic/3051_381.GIF" width="27" height="22"></td> <td><img border="0" src="pic/3051_382.GIF" width="77" height="49"></td> <td><img border="0" src="pic/3051_381.GIF" width="27" height="22"></td> <td><img border="0" src="pic/3051_383.GIF" width="87" height="27"></td> <td><img border="0" src="pic/3051_381.GIF" width="27" height="22"></td> <td><img border="0" src="pic/3051_384.GIF" width="127" height="27"></td> </tr> <tr> <td>牛二定律</td> <td><img border="0" src="pic/3051_381.GIF" width="27" height="22"></td> <td colspan="2"><img border="0" src="pic/3051_385.GIF" width="120" height="49"></td> <td> <p align="center"><img border="0" src="pic/3051_381.GIF" width="27" height="22"></td> <td colspan="2"><img border="0" src="pic/3051_386.GIF" width="150" height="49"></td> </tr> <tr> <td></td> <td colspan="3"> <p align="center">動能定理的微分形式</td> <td></td> <td colspan="2">動能定理的積分形式(有限形式)</td> </tr> </table> </td> </tr> <tr> <td width="20"><b><font color="#0000FF">二、</font></b></td> <td width="540"><b><font color="#0000FF">質點系的動能定理</font></b></td> </tr> <tr> <td width="20"></td> <td width="540"> <table border="0" cellpadding="0" cellspacing="0"> <tr> <td>將質系受力按主動力和約束力分，當為理想約束時，</td> <td><img border="0" src="pic/3051_387.GIF" width="82" height="29"></td> <td>，對上面二式</td> </tr> </table> </td> </tr> <tr> <td width="20"></td> <td width="540"> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="28%"> <p>求和，有微分形式：</td> <td width="22%"><img border="0" src="pic/3051_388.GIF" width="88" height="26"></td> <td width="25%"> <p align="right">積分形式：</td> <td width="25%"><img border="0" src="pic/3051_389.GIF" width="103" height="26"></td> </tr> </table> </td> </tr> <tr> <td width="20"></td> <td width="540"> <table border="1" cellpadding="0" cellspacing="0" bordercolor="#008080"> <tr> <td>問題：動能定理可求什么量？求幾個？用何種方程？</td> </tr> </table> </td> </tr> <tr> <td width="20"></td> <td width="540"><b>解題步驟：</b></td> </tr> <tr> <td width="20"></td> <td width="540"> (一)取研究對象（一般為整體，且不去約束，即不取分離體）；</td> </tr> <tr> <td width="20"></td> <td width="540"> (二)畫受力圖（只畫主動力，理想約束不做功）；</td> </tr> <tr> <td width="20"></td> <td width="540"> (三)列解方程。</td> </tr> <tr> <td width="20"></td> <td width="540"></td> </tr> <tr> <td width="560" colspan="2"> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="100%"> <table border="0" cellpadding="0" cellspacing="0" width="560"> <tr> <td>下面幾個例子都非常好</td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="50%"></td> <td width="50%" align="center" rowspan="8"><img border="0" src="pic/3051_394.GIF" width="249" height="188"></td> </tr> <tr> <td width="50%">例1 p164 典型例題</td> </tr> <tr> <td width="50%">圖示系統。</td> </tr> <tr> <td width="50%">均質滾子A、滑輪B重量和半徑均為Q和r，滾子純滾動，三角塊固定不動，傾角為α，重物重量P。</td> </tr> <tr> <td width="50%">求滾子質心C的加速度aC 。</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> <table border="0" cellpadding="0" cellspacing="0" width="108%"> <tr> <td width="42%">例2 p166 本題需用到較多運動分析</td> <td width="33%" rowspan="4"> <p align="center"><img border="0" src="pic/3051_395.GIF" width="247" height="184"></td> <td width="33%" rowspan="4"> <p align="center"><img border="0" src="pic/3051_396.GIF" align="left" width="84" height="204"></td> </tr> <tr> <td width="42%">如圖所示橢圓機構在鉛直面內運動。OC、AB為均質桿</td> </tr> <tr> <td width="42%">OC = AC = BC = l，OC重P，AB重2P，AB受一常力偶M，在圖示位置，θ= 30°，系統由靜止開始運動。求當A運動到O時A的速度vA 。滑塊質量不計，C為鉸鏈 。</td> </tr> <tr> <td width="42%"></td> </tr> </table> </td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="50%">例3 p168 典型例題，亦用到較多運動分析，較難</td> <td width="50%" rowspan="7"> <p align="center"><img border="0" src="pic/3051_397.GIF" width="227" height="223"></td> </tr> <tr> <td width="50%"></td> </tr> <tr> <td width="50%">均質細桿AB長l = 1.0m，重Q = 30N，上端靠在光滑鉛直面上，下端以鉸鏈A和均質圓柱中心相連，圓柱重P = 20N，半徑R = 0.4m，沿水平面純滾動。</td> </tr> <tr> <td width="50%">（1）當θ = 45°，若系統由靜止開始運動，求此時A點的加速度；</td> </tr> <tr> <td width="50%">（2）在該位置，若A點以速度vA = 1.0m/s向左運動，求該瞬時A點的加速度</td> </tr> <tr> <td width="50%"></td> </tr> <tr> <td width="50%"></td> </tr> </table> </td> </tr> <tr> <td> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td width="50%">例4 170 用動能定理建振動方程。</td> <td width="50%" rowspan="5"> <p align="center"><img border="0" src="pic/3051_398.GIF" width="259" height="172"></td> </tr> <tr> <td width="50%">圖示系統中，物塊A重P，均質圓輪B重Q，半徑為R，沿水平面純滾動，彈簧常數為k，初位置y = 0時，彈簧為原長，系統由靜止開始運動，滑輪D質量不計，繩不可伸長。</td> </tr> <tr> <td width="50%"></td> </tr> <tr> <td width="50%">試建立物塊A的運動微分方程，并求其運動規律。</td> </tr> <tr> <td width="50%"></td> </tr> </table> </td> </tr> </table> </td> </tr> </table> </td> </tr> <tr> <td width="560" colspan="2"> <p align="center"> <a href="3051_2.htm"><font color="#FF6666">[ 上一節 ]</font></a> <a href="3051_4.htm"><font color="#00CC00">[ 下一節 ]</font></a> </td> </tr> </table> </BODY></HTML> ?? 快捷鍵說明
復制代碼
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 + -