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认识浮力教学设计认识浮力教学设计 认识浮力 1(教学目标 ?知识与技能 ?知道什么是浮力及浮力产生的原因,知道浮力的大小跟哪些因素有关。 ?学习用弹簧测力计测浮力的大小。 ?过程与方法 ?通过实验与探究,感受浮力、认识浮力。 ?经历探究浮力的大小与哪些因素有关的过程,学习使用控制变量法。 ?情感态度与价值观 ?亲身参与科学探究的过程,在活动中大胆提出自己的猜想,能实事求是地记录数据,并根据实验数据提出自己的见解,有与他人合作交流的愿望。 2(教材说明 本节探讨浮力的初步知识,主要包括什么是浮力,怎样用弹簧测...

认识浮力教学设计
认识浮力教学 设计 领导形象设计圆作业设计ao工艺污水处理厂设计附属工程施工组织设计清扫机器人结构设计 认识浮力 1(教学目标 ?知识与技能 ?知道什么是浮力及浮力产生的原因,知道浮力的大小跟哪些因素有关。 ?学习用弹簧测力计测浮力的大小。 ?过程与方法 ?通过实验与探究,感受浮力、认识浮力。 ?经历探究浮力的大小与哪些因素有关的过程,学习使用控制变量法。 ?情感态度与价值观 ?亲身参与科学探究的过程,在活动中大胆提出自己的猜想,能实事求是地记录数据,并根据实验数据提出自己的见解,有与他人合作交流的愿望。 2(教材说明 本节探讨浮力的初步知识,主要包括什么是浮力,怎样用弹簧测力计测浮力,了解浮力产生的原因,探究浮力的大小跟什么因素有关。 浮力现象对学生来说并不陌生,但是学生根据生活现象得到的一些结论有些是片面的,本节让学生通过实验认识浮力,对于纠正学生的一些错误认识至关重要,同时用“称重法”认识浮力并定性探究浮力的大小与哪些因素有关,为后the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 面顺利探究阿基米德原理提供了知识和方法上的准备。另外了解了浮力的方向及产生的原因,也为进一步学习升力打下基础。 本节的编写思路是:首先通过一些生活中的现象,引起学生对浮力问题的关注,引发对“什么是浮力,浮力是怎样产生的”等问题的思考;接着教材设计了 “活动1”,通过一个简单的实验,让学生既能亲身感受到浮力的存在,从而得出浮力的概念,又能得出用弹簧测力计测量浮力的方法。然后设计了 “活动2”,引导学生利用液体压强的知识分析浮力的产生原因,使学生真正认识浮力的实质。最后定性研究浮力的大小与哪些因素有关,先让学生根据生活经验进行猜想,然后利用“称重法”进行实验探究,本节安排这个实验探究,不仅能使学生加深对浮力的认识,同时巩固了初中物理中最常用的测量浮力的方法――“称重法”; 而且为下一节探究阿基米德原理打下基础,减轻了下节“探究阿基米德原理”的教学内容,使教学难点分散。本节教材内容的编排循序渐进、环环相扣,步步深入,符合学生的认知规律。 本节教学重点:浮力概念贯穿全章,用弹簧测力计测浮力是本章各个探究实验的基础,所以浮力概念的建立和称重法测浮力是本节课教学的重点。 本节教学难点:研究浮力的产生原因,需要借助抽象的物理模型——液柱,还要综合应用压力、液体压强等知识,the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 因而对学生抽象思维能力和逻辑推理能力的要求都比较高;探究浮力的大小跟那些因素有关,涉及的因素较多,从猜想到设计实验、进行实验,开放性都比较强,因此这两个知识点是本节教学的难点。 3(教学建议 如前所述,学生对浮力现象虽然比较熟悉,但原有的生活经验产生的一些错误认识会不时干扰正常的学习,所以在教学中既要注意利用学生已有的经验和知识,又要注意通过实验纠正那些非科学的经验和观点。 关于课题的引入,教科书通过图片及相关文字说明,从生活现象出发,建立浮力的概念,符合学生的认知特点,也体现了新课标的理念:从生活走向物理。 在具体教学中,还可以采用以下几种引入方法: (1)播放录像:如鸭子、轮船漂在水面上;潜水艇在水中自由地上升和下潜;热气球载着重物飞上高空等。利用多媒体良好的视听效果使学生对浮力形成直觉认识,然后设问:这里面蕴含着哪些科学知识呢,让学生在领略大自然的美妙与和谐之中进入浮力的学习。 (2)演示一组有趣的实验,并请学生观察思考: ?黄色乒乓球浸没在水中,放手后逐渐上浮(乒乓球内可注入适量的水,这样上浮缓慢,便于观察)。 ?将铁皮浸没在水中,铁皮沉入水底;若将铁皮折成小the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 船,它却能浮在水面上。 ?把鸡蛋放在盛有清水的玻璃杯中,鸡蛋下沉;将鸡蛋取出,放入另一杯“水”(实际是盐水)中,鸡蛋却悬浮(或漂浮)。 ?用塑料袋(尽量找大一些、薄一些的)、细铁丝、浸有酒精的棉球,制作一个“热气球”,点燃后徐徐上升。 这样引入新课,不仅能创设一个良好的物理情景,而且能唤起学生的求知欲望,调动学生学习的积极性。 (3)做游戏:出示一个很深的量筒,把一个乒乓球放进去,要求不能把量筒倒过来,问:谁有办法把乒乓球取出,请一个学生演示:量筒加水后乒乓球上浮。再共同回忆“灌水取球”的 故事 滥竽充数故事班主任管理故事5分钟二年级语文看图讲故事传统美德小故事50字120个国学经典故事ppt ,思考:产生这一现象的原因是什么,把学生引到与浮力有关的问题上。 (4)边学边实验:让学生将木块投入烧杯的水中,将木块逐渐压入水底,然后放手。一是体会手的感觉;二是观察木块最终的情况。尝试回答:这些都说明了什么, 当学生对浮力有了一个粗略的认识后,可让同学们举例:生活中有还有哪些物体会受到浮力,将学生的思维进一步的发散,感受到物理就在我们的身边。 在上述教学过程中,学生可能出现的问题是,对物体的漂浮或上浮,同学们根据已有的经验都知道是浮力的作用;但对下沉的物体是否受到浮力,学生往往意见不一,由此可the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 过渡到下一个教学环节。 什么是浮力 如果学生在上一教学环节中没有提出“下沉的物体是否受到浮力”这一问题,可这样引入本部分教学:向学生展示金属块在水中下沉的情景,提出问题:浮在液面的物体受到浮力的作用,那么,石块、金属块等在水中下沉的物体受不受水的浮力呢,这样针对学生的思维障碍提出问题,造成悬念,使学生产生强烈的求知欲和好奇心,调动学生学习的积极性和主动性。 “活动1”的目的有两个:一是通过实验探究,让学生在触觉和视觉上感知到下沉的物体也受到浮力作用,从而纠正有关浮力的一些片面认识;二是得出用弹簧测力计测量浮力的方法。 “称重法”测浮力在探究浮力的大小跟什么因素有关和阿基米德原理时都要用到,因此,做好该实验是上好本节课,也是学好本章的关键,应组织所有学生动手操作,并留足时间,让学生在实验、观察中体验、发现、交流。 教学时可将学生分为几大组,分别用水和其他液体做同步实验,最后通过交流对比,得出结论。另外,为使实验结果明显,应选择量程较小(最大量程不超过5N)的弹簧测 3力计,金属块的体积至少超过10cm,还要提醒学生实验过程中要注意重物不能碰到容器底和侧壁。 the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 教材对活动1给出了比较完整的实验步骤,教学时也可通过下述演示,启发学生自行设计探究实验,以培养学生设计实验的能力和创新思维能力,例如: (1)把金属块挂在弹簧测力计下,观察弹簧测力计的示数; (2)用手轻轻地竖直向上托金属块,观察测力计的示数变化,思考:为什么产生这种现象, 通过实验,学生可得出如下结论:挂在弹簧测力计下的金属块浸没到水中后,弹簧测力计的示数变小了,说明:浸入水中的金属块受到水向上的托力,即受到水的浮力作用。换用酒精等其他液体做实验,可得到同样的结果。 关于浮力的方向,可以演示下面的实验帮助学生领会:找一段较粗的红毛线,将其两端分别固定在乒乓球和 F 大烧杯的底部,将水注入大烧杯,直到将乒乓球浸没,F 浮 观察红毛线被在竖直方向拉直;将大烧杯的一端垫高, 发现红毛线仍旧被在竖直方向拉直。此实验说明浮力 G 的方向总是竖直向上的。 图9-1 至此,学生确信:只要浸在液体中,物体就会受到液体竖直向上的浮力,引导学生 总结 初级经济法重点总结下载党员个人总结TXt高中句型全总结.doc高中句型全总结.doc理论力学知识点总结pdf 出浮力的定义,同时提醒他们注意:不仅浸在液体中的物体会受到浮力,浸在气体中的物体也会受到浮力,例如氢气球、热气球等。 关于“称重法”测浮力,教师可在活动1的基础上引导the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 学生思考:根据上述实验能否测出金属块受浮力的大小呢,然后在交流的基础上总结:物体所受浮力的大小等于物体的重力G(物体在空气中时弹簧测力计的示数)与物体浸在液体中时弹簧测力计的示数F之差,即:F=G-F。对部分仍浮 有困难的学生可通过分析物体受力帮助他们理解:如图9-1所示,挂在弹簧测力计下的金属块浸没到水中后,它受到重力G、水的浮力F和弹簧测力计的拉力F。金属块处于静止浮 状态,说明它受平衡力作用,有F+F =G,于是有F=G-F;浮浮力的方向应在一条直线上,即浮力向上且与重力在一条直线上,所以浮力的方向是竖直向上的。在上面学习的基础上进一步引导:由上面的分析,你是否找到测浮力的方法,然后让学生陈述“称重法”测浮力的步骤,使该方法得到落实。 浮力是怎样产生的 可用一个有趣的小实验引入本部分教学内容:取一只透明的塑料矿泉水瓶,其瓶口直径稍小于乒乓球的直径,去掉瓶底,将瓶口向下,把乒乓球放入塑料瓶内,使其正好盖住瓶口(若用小气球代替乒乓球,图9-2 实验更容易成功)。先请学生猜测:如果往瓶内注水,乒乓球会浮起吗,学生会答:会,因为要受到水的浮力。再往塑料瓶里面注水,如图9-2所示,学生观察到乒乓球被水压在瓶底而不上浮,诧异不已,议论纷纷。然后将塑料瓶口浸入烧杯的水中,使乒乓球下面有水,学生会看到乒乓球上浮,the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 又若有所悟。这样创设的情景,使学生产生强烈的好奇心,激起学生的探究欲望,同时通过感性认识,为下面理论分析浮力的产生原因打下基础。 还可以用下面的小实验引入:在烧杯底面和木块的一面涂上石蜡(或用蜡块代替木块,并使蜡面光滑)。将木块的光滑蜡面与烧杯光滑蜡面紧密接触,使水不能浸到接触面中间去。用手指压住木块,另一只手沿杯壁慢慢向烧杯中注水(此时不能让木块移动),请学生观察木块是否上浮;用铁丝撬动木块,使水渗入其底部,再请学生观察木块是否上浮。该实验成功的关键是要保证木块底部和容器底部必须十分平整、光滑。另外,为了消除学生认为是木块被容器底部粘住而不能上浮的认识,事先可把木块放在容器底部用力压住后再将容器倒置,放手后,木块就会脱离容器下落,说明容器没有粘住木块。 “活动2”的目的是通过理论分析,揭示浮力产生的原因。 要建立教材中的抽象物理模型——液柱,对学生来讲较为困难,可通过下面的演示实验帮助学生理解:用铁丝弯折成一个空心立方体,在六个面上扎上橡皮膜,使橡皮膜的松紧程度相同。当把它浸没在水中时,可以看到六个面的橡皮膜均向内凹进,而且前后左右面凹进的程度相同,而下表面比上表面凹进的程度要大。然后启发学生用液体压强与深度the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 的关系、二力平衡等知识分析:长方体左右两个侧面、前后两个侧面在水中的深度相同,因而受到水的压强相等,受到水的压力大小相等、方向相反,相互平衡;而长方体的上表面和下表面由于在水中的深度不同,受到水的压强大小不同,因而压力也不相等,下表面受到水的向上的压力F大下于上表面受到水向下的压力F。然后由学生归纳总结出:上 浮力是由于液体对物体向上和向下的压力差产生的。 注意,此处教学要求不宜过高,只要定性讨论出F>F下,使学生领会浮力是液体对物体向上和向下的压力之差就上 可以了,不要求进行有关计算。 浮力的大小跟哪些因素有关 该探究实验的目的,是研究浮力的大小跟哪些因素有关,并进一步消除学生对浮力的一些认识误区,为下一节探究阿基米德原理做好知识和方法上的准备。 ?猜想 在具体教学中,不必拘泥于教材的三个猜想,要让学生充分表述自己的想法。初中学生的思维较活跃,经过思考,学生会提出许多猜想,如: ?浮力大小跟物体的轻重有关。理由是轻的木块在水中会浮起来,而重的金属块则沉下去,说明木块所受浮力比金属块大。 ?浮力大小和物体体积有关。理由是:“你看~轮船体the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 积大,在海上载这么多的货物,说明它所受的浮力大。” ?浮力大小和液体的多少有关。理由是根据生活经验,在游泳池中游泳时感受到的浮力大,而在浴缸中洗澡时感受到的浮力小。 面对如此多的猜想,这时需要教师帮助学生去伪存真,把猜想合并归类。例如,第一种猜想“轻的木块在水中会浮起来,而重的金属块则沉下去”,这实际上是说“浮力的大小与物体的密度有关”;对于第二种猜想,要引导学生注意到所谓轮船体积大实质是浸入水中的体积大。 最后,可将猜想归纳:浮力的大小可能与物体的密度有关,与物体浸在液体中的体积大小有关;与物体浸入液体的深度有关;与液体的密度大小有关等。 (2)设计实验 可让学生分组讨论自行设计实验,大胆构思实验装置,然后对设计的方案进行全班交流,从科学性和可行性两个方面讨论、比较、质疑、完善。 教师应有意识地让学生分析:所设计实验的研究目的是什么,需要控制哪些条件,为渗透“控制变量法”的思想,提醒学生注意:浮力大小可能和上述因素都有关系,所以研究浮力大小和其中一个因素的关系时,必须控制其它因素,使其保持不变,以排除其它因素的影响和干扰。 (3)进行实验,与物体浸在液体中的体积大小有关;the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 与物体浸入液体的深度有关;等 为了节省时间,可根据不同的猜想,把学生分成若干小组,分别进行实验探究。除各组通用的器材外,对于验证“浮力的大小可能与物体的密度有关”的小组,教师还要为他们提供体积相同的铁块和铝块;对于验证“浮力的大小可能与液体的密度有关”的小组,教师还要为他们准备盐水或酒精。 学生用“控制变量法”进行实验,如: ?像教材图9-4那样,用线系住铁块,挂在弹簧测力计下,将铁块慢慢浸入水中的不同位置,观察到:当铁块逐渐浸入水中(从位置1?2?3)的过程中,弹簧测力计的示数会逐渐变小,这说明铁块受到的浮力逐渐变大。 ?当铁块全部浸没在水中(从位置3?4)后,弹簧测力计的示数不再变化,这说明铁块受到的浮力大小不变。 ?将铁块分别浸没在清水和盐水中的同一深度,发现铁块在清水中时弹簧测力计的示数较大,说明受到的浮力较小,在盐水中时弹簧测力计的示数较小,说明受到的浮力较大。 ?当把体积相同的铁块和铝块浸没在水中时,弹簧测力计减小的示数相同,这说明两个体积相同的金属块受到的浮力大小相同。 (4)得出结论 实验完毕,学生汇报实验数据,并通过分析论证,得出the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 结论。在学生分析实验数据时,教师可作以下提示(或说明):铁块全部浸没水中之前,铁块浸入液体的深度的改变实质是浸入液体中的体积的改变;铁块浸入液体中的体积就等于排开液体的体积。 通过对数据的分析比较,可得出如下结论:浸在液体里的物体受到的浮力的大小,跟物体排开液体的体积有关,跟液体的密度有关,而与物体的密度无关,与物体浸没在液体中的深度无关。 “想一想”的答案为:游泳者潜入水中时,排开水的体积比浮在水面上时大,所以受到浮力的变大。 这一活动的目的是借助生活实例,加深学生对影响浮力大小因素的理解,培养学生学以致用,解决问题的能力。具体教学中还可进一步启发学生举出类似的实例,拓展视野。 4(教学 评价 LEC评价法下载LEC评价法下载评价量规免费下载学院评价表文档下载学院评价表文档下载 ?课堂测评 1.一个盛有盐水的容器中悬浮着一个鸡蛋, 容器放在斜面上,如图9-3所示。图上画出了几个力的方向,你认为鸡蛋所受浮力的方向应当是 图9-3 ( ) A(F B(F C(F D(F 123 4 2.在一个密闭的真空玻璃罩里挂着一个弹簧测力计,测力计下挂一个体积较大的物体,物体静止。若将玻璃罩的开关the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom 打开,让空气进入,则此时( ) A(弹簧测力计的示数不变 B(弹簧测力计的示数将增大 C(弹簧测力计的示数将减小 D(弹簧测力计的示数可能增大也可能减小 3. 一铜块挂在弹簧测力计上,将铜块浸入水中时,弹簧测力计的示数等于( ) A(铜块的体积 B(铜块受到的重力 C(铜块受到的浮力 D(铜块受到的重力与浮力之差 4.一座桥墩,浸入水中10m,则桥墩受到的浮力为 N。 5.浸没在液体中的物体,其下表面受到的液体压强 上表面受到的液体压强(选填“大于”、“小于”或“等于”),物体受到的浮力就是液体对物体向上和向下的 。 6.如图9-4所示,小江同学用弹簧测力计测出物体的重力为10.0N。把物体完全浸没在水中,弹簧测力计的读数为8.5N,此时物体在水中所受浮力的大 图9-4 小为 N。 7.在探究“浮力的大小与哪些因素有关”时,某同学给出了下面两种现象,请根据现象提出合理的猜想。 the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom ?轮船从江河航行到大海,在海港加载一定质量的货物后与江河中吃水的深度相同。由此猜想:浮力可能与______________有关。 ?从井中提水,盛满水的桶露出水面越多,提桶的力就越大。由此猜想:浮力可能与___________有关。 【参考答案】 1(C 2(C ,(D ,(0 ,(大于 压 力差 ,(1.5 7(液体的密度 物体排开液体的体积 ?“自我评价与作业”指导 1.大 小 排开液体的体积 深度 2.C 3.答案是开放的,如把物体(体积稍大些)挂在较灵敏的弹簧测力计下,并将其放入真空罩中,记下测力计的示数,然后抽出真空罩中的空气,发现测力计的示数增大。 ?“课外活动”指导 涨起的气球受到一个向上的托力,说明气体对浸在其中的物体也会产生向上的浮力。 the same direction of rotation 90 ? or 180 ? for; after each disc rotor when measuring position alignment of the two half coupling constant, should also be in terms of accuracy and consistency. Surface deviation measurement, must in every 180 degrees corresponding to the two radii are equal to each other in order to eliminate errors caused by movement of the rotor. Only a support bearing of the rotor, WA couplings, such as the use of temporary leave the Center, should pay attention to keep the rotor in the measuring process in the center of the bearing oil retaining the nest does not change. Steam oil block, there should be sufficient clearance between the rotor and, in rotors make sure rotor is not on the block or seal oil. At the time of measurement, connections are not allowed between two rotors, each in a free State. Not allowed in case of assembled sleeve, Center work on the toothed coupling. Coupling tool should have adequate stiffness, installation must be secure and reliable. Coupling Center using a dial indicator, the table should be put in prison and avoid touching, to ensure correct measurement. Coupling disc after a week to return to the original position, circumference of dial gauge reading should be able to go back to the original value. When measuring the clearance of end, into the feeler of the gap should not exceed four at a time, when the gap is too large, you can use the gasket with the feeler gauge measurement of gauge blocks or finishing. bearing surface, markup should be in accordance with the mounting support pads, and retest the thickness. Once the lifting cylinder measurement of surface and internal cylinder surface height difference, compared with the original values confirm the location. Internal vertical and horizontal cylinder under state key insertion installation complex measuring cylinder in axial position. Bottom
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