[err:数据源标签'PE.DataSource id="cone" datasource="资料_内容页" itemId="126281" xslt="true" '返回数据错,原因:名称中不能包含“(”字符(十六进制值 0x28)。 行 21,位置 280。,源码:1262813 <meta http-equiv="refresh" content="0;url=/Item/126280.aspx" /> /Item/126280.aspx <meta http-equiv="refresh" content="0;url=/Item/126280.aspx" /> 14452020春人教版八年级物理下册全章教案:第十二章 简单机械1.55MB1.55Bdocczwlzx吴晓娟czwlzx/UploadFiles/UserPic/UserAvatars/15219_150_150.jpg <script language="JavaScript" type="text/JavaScript" src="/Common/GetHits.aspx?id=126281"></script> <script language="JavaScript" type="text/JavaScript" src="/Common/GetHits.aspx?hitstype=dayhits&id=126281"></script> <script language="JavaScript" type="text/JavaScript" src="/Common/GetHits.aspx?hitstype=weekhits&id=126281"></script> <script language="JavaScript" type="text/JavaScript" src="/Common/GetHits.aspx?hitstype=monthhits&id=126281"></script> <script language="JavaScript" type="text/JavaScript" src="/Common/GetBrowseTimes.aspx?id=126281"></script> <img src="/images/star4.jpg" /> 吴晓娟 0 2020春人教版八年级物理下册全章教案,简单机械2020年02月29日/UploadFiles/nopic.gif 五要素:一点、二力、两力臂.(1)“一点”即支点,杠杆绕着转动的点,用“O”表示.(2)“二力”即动力和阻力,它五要素:一点、二力、两力臂.(1)“一点”即支点,杠杆绕着转动的点,用“O”表示.(2)“二力”即动力和阻力,它们的作用点都在杠杆上.动力是使杠杆转动的力,一般用“F1”表示,阻力是阻碍杠杆转动的力,一般用“F2”表示.(3)“两力臂”即动力臂和阻力臂,动力臂即支点到动力作用线的距离,一般用“l1”表示,阻力臂即支点到阻力作用线的距离,一般用“l2”表示.3.杠杆的平衡(杠杆在动力和阻力作用下静止不动或匀速转动叫杠杆平衡)条件是动力×动力臂=阻力×阻力臂;公式:F1l1=F2l2.4.杠杆的应用(1)省力杠杆:l1>l2,F1<F2(省力费距离,如撬棒、铡刀、动滑轮、轮轴、羊角锤、钢丝钳、手推车、花枝剪刀).(2)费力杠杆:l1<l2,F1>F2(费力省距离,如人的前臂、理发剪刀 【内容简介】五要素:一点、二力、两力臂.(1)“一点”即支点,杠杆绕着转动的点,用“O”表示.(2)“二力”即动力和阻力,它们的作用点都在杠杆上.动力是使杠杆转动的力,一般用“F1”表示,阻力是阻碍杠杆转动的力,一般用“F2”表示.(3)“两力臂”即动力臂和阻力臂,动力臂即支点到动力作用线的距离,一般用“l1”表示,阻力臂即支点到阻力作用线的距离,一般用“l2”表示.3.杠杆的平衡(杠杆在动力和阻力作用下静止不动或匀速转动叫杠杆平衡)条件是动力×动力臂=阻力×阻力臂;公式:F1l1=F2l2.4.杠杆的应用(1)省力杠杆:l1>l2,F1F2(费力省距离,如人的前臂、理发剪刀、钓鱼竿).(3)等臂杠杆:l1=l2,F1=F2(不省力、不省距离,能改变力的方向.等臂杠杆的具体应用:天平.许多称质量的秤,如杆秤、案秤,都是根据杠杆原理制成的).二、滑轮1.滑轮是变形的杠杆.2.定滑轮(1)定义:中间的轴固定不动的滑轮.(2)实质:等臂杠杆.(3)特点:使用定滑轮不能省力但是能改变动力的方向.(4)对理想的定滑轮(不计轮轴间摩擦)F=G物.绳子自由端移动距离sF(或速度vF)=重物移动的距离sG(或速度vG)3.动滑轮五要素:一点、二力、两力臂.(1)“一点”即支点,杠杆绕着转动的点,用“O”表示.(2)“二力”即动力和阻力,它们的作用点都在杠杆上.动力是使杠杆转动的力,一般用“F <p><em>所属专辑:</em> <a href='/Special_261/Index.aspx' target='_blank'> 2020春人教版八年级物理下册全章教案 </a> </p> 下载地址1|ja/2020/2/202022992450.doc<p><span style="font-size:14px;font-family:宋体">五要素:一点、二力、两力臂.</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">(1)</span><span style="font-size:14px;font-family:宋体">“一点”即支点,杠杆绕着转动的点,用“O”表示.</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">(2)</span><span style="font-size:14px;font-family:宋体">“二力”即动力和阻力,它们的作用点都在杠杆上.动力是使杠杆转动的力,一般用“F<sub>1</sub>”表示,阻力是阻碍杠杆转动的力,一般用“F<sub>2</sub>”表示.</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">(3)</span><span style="font-size:14px;font-family:宋体">“两力臂”即动力臂和阻<img width="1" height="1" src="http://www.czwlzx.com/UEditor/themes/default/images/spacer.gif" alt="学科网(www.zxxk.com)--教育资源门户,提供试卷、教案、课件、论文、素材及各类教学资源下载,还有大量而丰富的教学相关资讯!" style="background:url(http://www.czwlzx.com/UEditor/themes/default/images/word.gif) no-repeat center center;border:1px solid #ddd" />力臂,动力臂即支点到动力作用线的距离,一般用“l<sub>1</sub>”表示,<img width="2" height="2" src="http://www.czwlzx.com/UEditor/themes/default/images/spacer.gif" alt="学科网(www.zxxk.com)--教育资源门户,提供试卷、教案、课件、论文、素材及各类教学资源下载,还有大量而丰富的教学相关资讯!" style="background:url(http://www.czwlzx.com/UEditor/themes/default/images/word.gif) no-repeat center center;border:1px solid #ddd" />阻力臂即支点到阻力作用线的距离,一般用“l<sub>2</sub>”表示.</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">3.</span><span style="font-size:14px;font-family:宋体">杠杆的平衡(杠杆在动力和阻力作用下静止不动或匀速转动叫杠杆平衡)条件是动力×动力臂=阻力×阻力臂;公式:F<sub>1</sub>l<sub>1</sub>=F<sub>2</sub>l<sub>2</sub>.</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">4.</span><span style="font-size:14px;font-family:宋体">杠杆的应用</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">(1)</span><span style="font-size:14px;font-family:宋体">省力杠杆:l<sub>1</sub>&gt;l<sub>2</sub>,F<sub>1</sub>&lt;F<sub>2</sub>(省力费距离,如撬棒、铡刀、动滑轮、轮轴、羊角锤、钢丝钳、手推车、花枝剪刀).</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">(2)</span><span style="font-size:14px;font-family:宋体">费力杠杆:l<sub>1</sub>&lt;l<sub>2</sub>,F<sub>1</sub>&gt;F<sub>2</sub>(费力省距离,如人的前臂、理发剪刀、钓鱼竿).</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">(3)</span><span style="font-size:14px;font-family:宋体">等臂杠杆:l<sub>1</sub>=l<sub>2</sub>,F<sub>1</sub>=F<sub>2</sub>(不省力、不省距离,能改变力的方向.等臂杠杆的具体应用:天平.许多称质量的秤,如杆秤、案秤,都是根据杠杆原理制成的).</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">二、滑轮</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">1.</span><span style="font-size:14px;font-family:宋体">滑轮是变形的杠杆.</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">2.</span><span style="font-size:14px;font-family:宋体">定滑轮</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">(1)</span><span style="font-size:14px;font-family:宋体">定义:中间的轴固定不动的滑轮.</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">(2)</span><span style="font-size:14px;font-family:宋体">实质:等臂杠杆.</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">(3)</span><span style="font-size:14px;font-family:宋体">特点:使用定滑轮不能省力但是能改变动力的方向.</span></p><p style="line-height:21px"><span style="font-size:14px;font-family:宋体">(4)</span><span style="font-size:14px;font-family:宋体">对理想的定滑轮(不计轮轴间摩擦)F=G<sub>物</sub>.绳子自由端移动距离s<sub>F</sub>(或速度v<sub>F</sub>)=重物移动的距离s<sub>G</sub>(或速度v<sub>G</sub>)</span></p><p><span style="font-size:14px;font-family:宋体">3.</span><span style="font-size:14px;font-family:宋体">动滑轮</span></p><p><br /></p>人教版不限教案免费doc <img src="/images/nopic.gif" alt="2020%e6%98%a5%e4%ba%ba%e6%95%99%e7%89%88%e5%85%ab%e5%b9%b4%e7%ba%a7%e7%89%a9%e7%90%86%e4%b8%8b%e5%86%8c%e5%85%a8%e7%ab%a0%e6%95%99%e6%a1%88%ef%bc%9a%e7%ac%ac%e5%8d%81%e4%ba%8c%e7%ab%a0+%e7%ae%80%e5%8d%95%e6%9c%ba%e6%a2%b0" border="0" /> /UploadFiles/ja/2020/2/202022992450.doc <script type="text/javascript" src="/cuplayer4/js/swfobject.js"></script> <div class="video" id="CuPlayer"><b><img src="/cuplayer4/images/loading.gif" /> 网页视频播放器加载中,请稍后...<a href="http://www.cuplayer.com/cuplayer" target="_blank">点此升级>></a></b></div> <script type="text/javascript"> var so = new 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