游戏导入：请两位同学上讲台来测试反应快慢，具体要求：老师捏住一把长尺的上端，学生用一只手在0刻度处做捏住的准备，手不能碰到直尺。当看到老师放开尺子时立即捏住尺子，测出直尺降落的高度。可以根据这个高度比较二人的反应快慢。

学生活动：同桌之间相互测试各自的反应长度，并且将数据记录到表格里。

教师提问：我们可以通过比较这个高度看出这两位同学谁反应快，但能不能根据这个高度来测出他们的反应时间呢？我们来学习本节课内容——《自由落体运动》

通过男生与女生反应快慢的比赛调动学生的积极性，激起学生学习的兴趣。

新课教学：

1、自然界里的落体运动：

展示图片：1、蹦极运动；

2、流星、3、蹦床运动；

3、跳水运动；5、树叶飘落；6、下雨...

可让学生再举几个落体运动的例子，同时指出刚才直尺的运动也是下落运动。

用大量的图片让学生建立起落体运动的感性认识。

一、 谁落得更快呢？

教师：关于落体运动，人们关注的是哪个落得快一些，我们观察一下下面的实验。

演示实验：羽毛的下落与铁片的下落，注意从同一高度释放。为了保证这一点，采用下面的装置：

用铁架台固定一铁片，用磁铁吸住羽毛和铁片，往上拔磁铁，羽毛与铁片就会同时且初速为0下落。

学生活动：观察并且分析现象，得结论：重的比轻的落得快。

教师：这样，我们会发现物体下落的快慢和其质量有关，那么，能否利用课前让你们准备的小物件设计一些实验证明这一点呢？

学生设计实验，器材：一元硬币两枚，一角硬币两枚，白纸两张，剪刀一把。

可能方案预测：

1、硬币与相同大小的纸片的下落比较，结论支持上述观点；

2、一元硬币与一角硬币的下落比较，轻重一样快；

3、相同重的纸片与纸团的下落比较，质量相同快慢不一样；

4、重的纸片与轻的纸团的下落比较，轻的快；

学生的实验会表明质量大小与物体下落的快慢无关。

教师：那么为什么羽毛比铁片落得慢呢？

这样设计体现了一种严谨性。

鼓励学生从各个角度设计实验，最后让具有代表性的小组交流汇报。

学生讨论分析，可得出是空气在作怪的结论。

教师总结：空气作为一种流体，对下落的物体会有阻力的作用，阻力大小和物体的大小有关，羽毛轻、面积大，所受阻力对它的影响相对大，所以落得慢了。如果我们能在一个没有空气的地方看一下它们的下落，会怎样呢？

学生：一样快。

教师：接下来，我们看一下下面的实验。

演示牛顿管实验。

可以拿两根相同的牛顿管演示，一根有空气，一根提前抽成真空（接近真空），对学生进行说明，让学生观察现象，体会空气对物体下落的影响。

教师：下落的物体，如果考虑到空气对它的作用，研究它时情况会变得很复杂；如果只考虑关键因素——重力的影响，那么问题变得就简单了。这种运动就是我们本节课重点学的——自由落体运动。

让学生体会到空气在物体下落过程中的作用，并清楚某些情况下这种阻力作用影响可忽略。

体现抓住本质因素、忽略次要因素的思想。

二、 自由落体运动

定义：物体只在重力作用下从静止开始下落的运动。

说明：在有空气的地方，如果空气作用比较小，物体的下落也可近似认为是自由落体运动。

例如：羽毛的下落不是自由落体运动，铁片的下落可认为是自由落体运动。

思考：自由落体运动是什么样的运动呢？                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     

教师：数据背后往往反映了某种物理机制，我们可以研究一些数据之间的关系，看看它们满足什么物理公式，从而发现规律。这种方法是物理学家经常采用的，我们试着也采用这种方法研究一下自由落体运动。

教师：幻灯片展示的是一组有关自由落体的位移、速度和时间关系的数据，同学们可以看看位移与时间、速度与时间之间满足什么关系式？     

学生活动：尝试着寻找这些数据的关系。

学生首先会发现速度与时间的关系：      v=9.8t

引导学生发现位移与时间的关系：        x=4.9t²

这种关系恰好满足匀变速直线运动的规律：

其中，v₀ = 0

    a=9.8

由此可以知道。自由落体运动是初速度为0的匀加速直线运动。

这里没有采用教材提供的实验，而是采用利用数据分析规律的方法，这样可以避免这节课过多实验的弊端，节约了时间，同时让学生也能领会到另外一种物理方法。

根据数据发现位移与时间的关系式时，学生可能想不到，注意引导。

四、自由落体运动的规律：

1、自由落体加速度：在同一个地方，这个加速度是恒定的，观察表格，看看它与什么因素有关？

学生活动：观察自由落体加速度的数据，会发现其大小与纬度高低有关。记下这个规律，待学了后面知识解决原因。

2、符号：g。

3、重力加速度的大小：

g=9.8m/s2 或 g=10m/s2

4、重力加速度的方向：竖直向下。

这里的规律可以教师直接介绍。

5、运动规律：v₀=0,a=g

学生自己导出这些规律。

怎样估测这幢教学楼的高度？

五、课堂活动

1、计算刚才两位同学的反应时间，或根据自己的降落长度计算自己的反应时间；

2、如何估算学校教学楼的高度？需要哪些器材？实验步骤是什么？

利用已学规律解决自己身边的一些问题，可以巩固知识，培养兴趣。

六、课后作业：

1、课本45页1-4题做到作业本上；

2、本周到实验室，通过做实验，得出研究自由落体运动性质。

第2个作业是开放性的，目的是让学生亲自做教材上设计的实验，获得第一手资料。