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ID:48743352
大小:3.99 MB
页数:19页
时间:2020-01-21
《邢秀娜竖直方向圆周运动中的向心力.ppt》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、CentripetalForce向心力Circlesatamusementparks游乐场中的竖直圆周运动.理综组邢秀娜UniformCircularMotionUniformcircularmotion(匀速圆周运动)occurswhenthespeed(速率)ofanobjectexperiencingcircularmotionremainsconstant.Isvelocity(速度)constantforuniformcircularmotion?No.Thevelocityisalwayschangingdirection.知识
2、回顾(匀速圆周运动)why演示线的一端系一小球,使小球在光滑水平面上作匀速圆周运动uniformcircularmotion。一、什么叫向心力CentripetalForce?观察并思考:1、小球的受力情况如何?(drawfreebodydiagram)2、线的拉力方向(direction)有何特点?想一想:向心力的方向direction是否改变?迫使物体做匀速圆周运动,方向总是沿半径指向圆心的力叫向心力。注意:向心力是从力的作用效果命名的OFFFVVVO分析:结论:向心力的方向(direction)是在不断变化(change)的Non-U
3、niformMotion非匀速圆周运动(重点)Accelerating(加速)intotheloopthefirsttime.Atthetopoftheloop,thecarwillexperienceFc=Fg+FN.Whichforcesarecentripetalforces?Normalforce(正交反作用力)andweight引力.谁来提供向心力?Whatifthecargoesaroundasecondtime?Andweonlyusetheforceofgravity(引力)astheacceleratingforce?Su
4、pposethecarmovesmoreslowly,sothatFc=Fg.Thetrackdoesn’texertFNonthecartokeepitmovingonthetrack.Whatifthecarmovestooslowly?TheFc5、gravity.Fc=FgWhatabouttension(张力)?TopofCircleWhichforcesarecentripetal?FgandFT.So:Fc=Fg+FTSidesofthecircleWhichforcesarecentripetal?OnlyFTisFc.So,Fc=FTWhichforcesarecentripetal?FTandFgNow,Fgisn’tdirectedtowardsthecentre,butit’sparallel–intheoppositedirection.Fc=FT-FgCentri6、petalForce(F=ma)Newton’sSecondLawofMotion牛顿第二定律Fc=mv2/rFc=mrω2Practice1Abucketofwaterwithamassof1.5kgisspuninaverticalcircleonarope.Theradiusofthecircleis0.75mandthespeedofthebucketis3.00ms-1.WhatisthetensionontheropeinpositionC?
5、gravity.Fc=FgWhatabouttension(张力)?TopofCircleWhichforcesarecentripetal?FgandFT.So:Fc=Fg+FTSidesofthecircleWhichforcesarecentripetal?OnlyFTisFc.So,Fc=FTWhichforcesarecentripetal?FTandFgNow,Fgisn’tdirectedtowardsthecentre,butit’sparallel–intheoppositedirection.Fc=FT-FgCentri
6、petalForce(F=ma)Newton’sSecondLawofMotion牛顿第二定律Fc=mv2/rFc=mrω2Practice1Abucketofwaterwithamassof1.5kgisspuninaverticalcircleonarope.Theradiusofthecircleis0.75mandthespeedofthebucketis3.00ms-1.WhatisthetensionontheropeinpositionC?
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