杠杆平衡条件教案

杠杆平衡条件 《杠杆的平衡条件》 【教学目标】 一、知识与技能 知道什么是杠杆，能从常见的工具和简单机械中识别出杠杆;理解支点、阻力、阻力臂、动力、动力臂;知道杠杆平衡的条件;能根据实际需要正确选择和使用杠杆。 二、与过程 经历“探究杠杆平衡条件”的过程，参与科学探究活动，体验科学探究的全过程。培养学生的观察力、创造想象力;实验操作能力和数据处理能力;能根据自己制定的分类原则给杠杆分类;学习分类的方法。 三、情感态度价值观 体验科学探究的乐趣，激起学生学习物理的兴趣，培养学生认真、细致和实事求是的科学态度。了解杠杆在我国古代的应用。 【教学难点】 1.设计“探究杠杆平衡条件”的实验方案; 2(力臂的确定( 【教学重点】 探究杠杆平衡条件。 【教学方法】 实验探究，引导创新。 【教学过程】 一、引入新课 同学们，我是阿基米德，已经两千多岁。在两千多年前，我说过“给我一个支点，我可以撬动地球。”两千多年来，我没有将地球撬动，这是事实，这并不是我的错，因为我没有找到一个合适的支点。可是，许多爱嚼舌头的人硬说我是在吹大话，在说谎。我这个两千多methods of the poker vibrator vibrating, steel reinforcement in Foundation pit West of a steel processing plant concentrates production templates using large pieces of shaped steel formwork and bamboo glue formwork methods. Bridge jacking of 500t hydraulic top picks, roof is complete, edge angle wall, railing, cable channel, u-channel and other ancillary works construction. 3.1.4. the construction process (see the construction process flow chart) construction process flow chart3.2. construction site layout 3.2.1. construction site layout 1, layout according to the construction design requirement, Foundation placed in the North of the line. Construction site layout as shown in Figure 1. construction general layout. 2, temporary works combined with the devoted section personnel and machinery equipment, the actual situation, in accordance with the specification requirements, established in the site layout construction and management required from near, and to meet the normal production and life in the Office, housing and steel processing facilities, warehouse and storage and the template field, and fire facilities as required. Separation of work zones, work area, living area settings, and set wall closed. 3, construction water water in situ dewatering wells, water tanks and bottled water. 4, the construction of electricity given this project of welded steel and concrete construction 岁的人实在受不了这样的委屈。今天，我请大家帮我伸冤，你们愿意吗,不管结果如何，我??阿基米德先在这谢谢大家了～ 大家有信心吗, 要想帮我伸冤，实际很容易，只需弄清杠杆的平衡条件即可。 二、新授 (板书)第一节 科学探究:杠杆的平衡条件 杠杆是一种古老而简单的机械，许许多多机械的应用改变和丰富了我们的生活。今天我们就从生活中的杠杆说起，了解机械与人的关系。 (板书)1(认识杠杆 让学生展示自带的杠杆(铁锤、剪刀、轮轴、扳子、钢丝钳、镊子等)并说出其应用及特征。 讨论、归纳各种杠杆的共同特征: (板书)在力的作用下，能绕某一固定点转动的硬棒，物理学中叫杠杆。 置疑:古猿要把大石块移动，用木棍捅石块捅不动，谁能想法帮帮它, 置疑:古猿用的木棍是杠杆吗, 铁锤、剪刀、轮轴、扳子、钢丝钳、镊子等是不是杠杆, 置疑:为什么人们利用杠杆橇石块时总是把支点放在离石块很近的地方,而不放到离石块远一些的地方, (板书)2(认识杠杆的几个概念 介绍支点、动力、动力臂、阻力、阻力臂。 methods of the poker vibrator vibrating, steel reinforcement in Foundation pit West of a steel processing plant concentrates production templates using large pieces of shaped steel formwork and bamboo glue formwork methods. Bridge jacking of 500t hydraulic top picks, roof is complete, edge angle wall, railing, cable channel, u-channel and other ancillary works construction. 3.1.4. the construction process (see the construction process flow chart) construction process flow chart3.2. construction site layout 3.2.1. construction site layout 1, layout according to the construction design requirement, Foundation placed in the North of the line. Construction site layout as shown in Figure 1. construction general layout. 2, temporary works combined with the devoted section personnel and machinery equipment, the actual situation, in accordance with the specification requirements, established in the site layout construction and management required from near, and to meet the normal production and life in the Office, housing and steel processing facilities, warehouse and storage and the template field, and fire facilities as required. Separation of work zones, work area, living area settings, and set wall closed. 3, construction water water in situ dewatering wells, water tanks and bottled water. 4, the construction of electricity given this project of welded steel and concrete construction 强调力臂的画法: ?找支点; ?画出动力和阻力的作用线; 过支点向力的作用线作垂线，垂线的长度即是力臂。 ? 概括为:一找点二画线三作垂线段。 用橡皮、笔、书、直尺设计一个杠杆探究支点在不同位置时动力的大小情况。 结论:动力臂越长、阻力臂越短，越省力;动力臂越短、阻力臂越长，越费力。 所以人们为了用较小的力撬大石块时，就要把支点放到离石块较近的地方，增大动力臂、减小动力。 (1)提出问大家能否猜想一下动力、动力臂、阻力、阻力臂之间的关系呢, (板书)3(杠杆的平衡条件 (2)猜想与假设让学生充分猜想，同时用橡皮、小刀、直尺、硬币等物示意给学生看，什么叫杠杆的平衡。 学生可能给许多种猜想如: ?F+L=F+L?F/L=F/L ?F-L=F-L?F×L=F×L 1122 11221122 1122 教师带领学生分析以上猜想，甄别那是明显错误的猜想，如?F+L=F+L?F-L=F-L，1122 1122methods of the poker vibrator vibrating, steel reinforcement in Foundation pit West of a steel processing plant concentrates production templates using large pieces of shaped steel formwork and bamboo glue formwork methods. Bridge jacking of 500t hydraulic top picks, roof is complete, edge angle wall, railing, cable channel, u-channel and other ancillary works construction. 3.1.4. the construction process (see the construction process flow chart) construction process flow chart3.2. construction site layout 3.2.1. construction site layout 1, layout according to the construction design requirement, Foundation placed in the North of the line. Construction site layout as shown in Figure 1. construction general layout. 2, temporary works combined with the devoted section personnel and machinery equipment, the actual situation, in accordance with the specification requirements, established in the site layout construction and management required from near, and to meet the normal production and life in the Office, housing and steel processing facilities, warehouse and storage and the template field, and fire facilities as required. Separation of work zones, work area, living area settings, and set wall closed. 3, construction water water in situ dewatering wells, water tanks and bottled water. 4, the construction of electricity given this project of welded steel and concrete construction 力和力臂单位不一样是不能加减的。 将学生分成两部分分别探究?F/L=F/L?F×L=F×L 1122 1122 (3)制定计划与设计实验 设计实验方案:(引导学生讨论，实验装置中力的大小、力臂的大小最好能随时知道。实验探究前，应让学生充分讨论他们的探究方案。) 实验目的: 探究杠杆的平衡条件 实验器材: 杠杆、铁架台、钩码 实验步骤: ?如图，把杠杆的中点支在铁架台上，调节杠杆两端的平衡螺母，使杠杆在水平位置平衡; ※为什么要求杠杆静止时，在水平位置呢,(因为这样力臂的数值在杠杆上就能直接读出或量出() ※ 调节杠杆平衡的方法:左沉右旋 右沉左旋 ?在杠杆两边挂适当钩码，并移动钩码位置，使杠杆在水平位置再次平衡，计算两力的大小，并读出两力臂的值，将力和力臂的数值填入表中;(重复3次) (4)进行实验与收集证据 实验次数 F/N L/cm F/N L/cm 1122 1 2 3 分析判断:在分析判断过程中有可能出现F+L=F+L的结论，要求学生认真分析数据，1122 找到出错的原因，为以后的学习和工作打下坚实的基础。 methods of the poker vibrator vibrating, steel reinforcement in Foundation pit West of a steel processing plant concentrates production templates using large pieces of shaped steel formwork and bamboo glue formwork methods. Bridge jacking of 500t hydraulic top picks, roof is complete, edge angle wall, railing, cable channel, u-channel and other ancillary works construction. 3.1.4. the construction process (see the construction process flow chart) construction process flow chart3.2. construction site layout 3.2.1. construction site layout 1, layout according to the construction design requirement, Foundation placed in the North of the line. Construction site layout as shown in Figure 1. construction general layout. 2, temporary works combined with the devoted section personnel and machinery equipment, the actual situation, in accordance with the specification requirements, established in the site layout construction and management required from near, and to meet the normal production and life in the Office, housing and steel processing facilities, warehouse and storage and the template field, and fire facilities as required. Separation of work zones, work area, living area settings, and set wall closed. 3, construction water water in situ dewatering wells, water tanks and bottled water. 4, the construction of electricity given this project of welded steel and concrete construction (5)讨论、交流、合作 你的实验结论与你的假设一致吗,你的结论是什么, (6)得出结论:杠杆的平衡条件是: 动力×动力臂,阻力×阻力臂 (F×L=F×L) 1122 (板书)4(杠杆的分类 告诉学生分类首先要制定分类原则，然后按原则分类。 无论学生怎样分类，只要符合分类原则，都应充分肯定。 5(作业设计: 在如图所示的实验装置中: methods of the poker vibrator vibrating, steel reinforcement in Foundation pit West of a steel processing plant concentrates production templates using large pieces of shaped steel formwork and bamboo glue formwork methods. Bridge jacking of 500t hydraulic top picks, roof is complete, edge angle wall, railing, cable channel, u-channel and other ancillary works construction. 3.1.4. the construction process (see the construction process flow chart) construction process flow chart3.2. construction site layout 3.2.1. construction site layout 1, layout according to the construction design requirement, Foundation placed in the North of the line. Construction site layout as shown in Figure 1. construction general layout. 2, temporary works combined with the devoted section personnel and machinery equipment, the actual situation, in accordance with the specification requirements, established in the site layout construction and management required from near, and to meet the normal production and life in the Office, housing and steel processing facilities, warehouse and storage and the template field, and fire facilities as required. Separation of work zones, work area, living area settings, and set wall closed. 3, construction water water in situ dewatering wells, water tanks and bottled water. 4, the construction of electricity given this project of welded steel and concrete construction (1)实验前没有挂钩码时，发现杠杆左边下倾，这时可以将杠杆右端的螺母向 边 旋一些，使杠杆水平平衡。 (2)实验时只有8个相同的钩码，杠杆上的点是等间距的，当在A点挂4个钩码时，则 怎样挂钩码可以使杠杆水平平衡,请设计出两种方案。 (1) ; (2) 。 methods of the poker vibrator vibrating, steel reinforcement in Foundation pit West of a steel processing plant concentrates production templates using large pieces of shaped steel formwork and bamboo glue formwork methods. Bridge jacking of 500t hydraulic top picks, roof is complete, edge angle wall, railing, cable channel, u-channel and other ancillary works construction. 3.1.4. the construction process (see the construction process flow chart) construction process flow chart3.2. construction site layout 3.2.1. construction site layout 1, layout according to the construction design requirement, Foundation placed in the North of the line. Construction site layout as shown in Figure 1. construction general layout. 2, temporary works combined with the devoted section personnel and machinery equipment, the actual situation, in accordance with the specification requirements, established in the site layout construction and management required from near, and to meet the normal production and life in the Office, housing and steel processing facilities, warehouse and storage and the template field, and fire facilities as required. Separation of work zones, work area, living area settings, and set wall closed. 3, construction water water in situ dewatering wells, water tanks and bottled water. 4, the construction of electricity given this project of welded steel and concrete construction