📄 3051_3.htm
字号:
<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 动能定理</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">质点的动能定理</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">动能定理的微分形式</td> <td></td> <td colspan="2">动能定理的积分形式(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">质点系的动能定理</font></b></td> </tr> <tr> <td width="20"></td> <td width="540"> <table border="0" cellpadding="0" cellspacing="0"> <tr> <td>将质系受力按主动力和约束力分，当为理想约束时，</td> <td><img border="0" src="pic/3051_387.GIF" width="82" height="29"></td> <td>，对上面二式</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">积分形式：</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>问题：动能定理可求什么量？求几个？用何种方程？</td> </tr> </table> </td> </tr> <tr> <td width="20"></td> <td width="540"><b>解题步骤：</b></td> </tr> <tr> <td width="20"></td> <td width="540"> (一)取研究对象（一般为整体，且不去约束，即不取分离体）；</td> </tr> <tr> <td width="20"></td> <td width="540"> (二)画受力图（只画主动力，理想约束不做功）；</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>下面几个例子都非常好</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 典型例题</td> </tr> <tr> <td width="50%">图示系统。</td> </tr> <tr> <td width="50%">均质滚子A、滑轮B重量和半径均为Q和r，滚子纯滚动，三角块固定不动，倾角为α，重物重量P。</td> </tr> <tr> <td width="50%">求滚子质心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 本题需用到较多运动分析</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%">如图所示椭圆机构在铅直面内运动。OC、AB为均质杆</td> </tr> <tr> <td width="42%">OC = AC = BC = l，OC重P，AB重2P，AB受一常力偶M，在图示位置，θ= 30°，系统由静止开始运动。求当A运动到O时A的速度vA 。滑块质量不计，C为铰链 。</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 典型例题，亦用到较多运动分析，较难</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%">均质细杆AB长l = 1.0m，重Q = 30N，上端靠在光滑铅直面上，下端以铰链A和均质圆柱中心相连，圆柱重P = 20N，半径R = 0.4m，沿水平面纯滚动。</td> </tr> <tr> <td width="50%">（1）当θ = 45°，若系统由静止开始运动，求此时A点的加速度；</td> </tr> <tr> <td width="50%">（2）在该位置，若A点以速度vA = 1.0m/s向左运动，求该瞬时A点的加速度</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 用动能定理建振动方程。</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%">图示系统中，物块A重P，均质圆轮B重Q，半径为R，沿水平面纯滚动，弹簧常数为k，初位置y = 0时，弹簧为原长，系统由静止开始运动，滑轮D质量不计，绳不可伸长。</td> </tr> <tr> <td width="50%"></td> </tr> <tr> <td width="50%">试建立物块A的运动微分方程，并求其运动规律。</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">[ 上一节 ]</font></a> <a href="3051_4.htm"><font color="#00CC00">[ 下一节 ]</font></a> </td> </tr> </table> </BODY></HTML> ⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -