英国高中物理教材“牛顿运动定律”赏析

速度在特定时段内持续稳定地转变，这种情形下，

物体的质量若保持恒定，则能用m来代表m1和m2，这种情况下无需区分，两者数值相同，可以直接替换，简化计算过程，提高分析效率。

物体运动状态发生改变，因此：                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

选定一个固定数值k，由此可导出：                                →       F等于k乘以m乘以a

牛顿确定，当质量为1千克的物体产生每秒每秒一米的加速度时，这种力的大小即为一个牛顿，

这表明k等于一个,因此:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

所以，施加在车辆上的均等力量要等于：1449千克乘以6.88米每二次方秒，结果为9970牛顿

一次意外事件里，施加在车辆及乘员身上的作用力远远超出9970牛顿，假如一辆兰博基尼遭遇撞击，它的行驶速度会在不到百分之一秒内从每小时六十英里（相当于每秒26.8米）骤降至零，此刻它的减速度为：

施加在车辆上的均等力量为：F=ma=1449公斤×（－268）米每二次方秒=－390 000牛顿

其中负号表明这个力的方向与速度的方向相反，是阻碍汽车的力。

碰撞发生时，即便车辆行驶速率不高，其变化率也能达到200米每平方秒，这个数值是重力加速度的二十倍，换言之，施加在乘客身上的力量将相当于其体重的二十倍。

英国教材在讲解牛顿运动定律时，所有知识点都依托于一个实际背景，那就是围绕汽车安全问题展开，这种主题式设计贯穿整个章节，每个概念都不是单独呈现，而是融入了与汽车相关的具体案例之中。通常先从较为繁杂的实际状况入手，然后提炼出标准的物质模型，接着形成严谨的物理认识，再将其推向外部世界加以运用，这实际上是一个逐步深入剖析的步骤，最终让知识要点得以显现。这种做法与建构主义倡导的“通过挑战难题来掌握知识”的理念完全吻合。这一片开阔的景象，以及它同日常生活的紧密关联，让学生能够真切体会到物理就在身边，学习这门学科确实很有价值，进而有助于点燃他们学习物理的热情，培养他们喜欢物理的情怀。

本章围绕英国社会不可或缺的出行工具“汽车”展开，以“车辆相撞”、“行车安全”以及“怎样保障乘客安全”等实际议题为脉络，引导学生在贴近现实的环境里分析情况或处理事务，借此实现知识的自我习得，物理学原理与STS-EL议题紧密结合，达成了实质性的“融入”。

英国教材倾向于在学生熟悉的生活场景里介绍原理，阐明公理，借助原理分析日常事务，演示公式的基本运用和运算，对原理和公理的深度探讨并不强调。以本章为例开元棋官方正版下载，总共列出了12个原理，仅用13页纸，但书中涵盖的内容相当丰富。阐述了空气流动的阻碍效应,人的行动迟缓程度,车辆行进时的空间间隔,汽车上防止相撞的装置,车辆制动操作的构造等概念,使物理学与日常现象、科技发展及不同领域产生了紧密联系,书本里的知识比较贴近人们的实际生活,富有时代气息。

英国教材这一章布置了11个课堂练习题，另外还有5道已经考过的题目。这些习题的设置比较灵活，其中涉及的运算也不算复杂，不过每一道题都放在了现实情境下，跟日常生活、社会状况以及科学技术联系紧密，这样容易让学生产生学习的热情和探索知识的欲望。例如第3个问题提出，有些看法认为，成年人抱着的小孩在车里出行会更为安全。测量紧抱一个10公斤的幼儿时需施加的力度开元ky888棋牌官方版，例如。探讨为何高速公路的防撞设施在车辆撞击下会轻易弯曲，而利用牛顿第二定律说明这种设计为何比难以变形的坚固护栏更为安全。

英国教材中随处流露着人文观念和情感引导。比如第八章的三个小节名称分别是“守护生命”、“妥当停驻”、“留意相撞”，完全没有提及物理术语，表面上看是一篇关怀生命、增强汽车安全的科普文章，缺少了物理课本应有的庄重感，却洋溢着人文精神的味道。书本内容里到处体现着人文精神，列举了不少极具煽动性的口号、提醒，例如“要夺走你的生命开元ky888棋牌官网版，而非孩子的性命”、“在推广系安全带的全国性活动中，交通管理部门发布通知：‘在一场交通事故里，后座上的成年人会被十五公斤的推力向前甩出，这个推力相当于一头大象的分量’……”这些经典宣传话语的运用，在潜移默化中提升了学生的社会责任感和参与意识，有助于他们形成主人翁精神，塑造独立的人格，整个过程完全没有说教意味。

他山之石可以攻玉，英国教材很多可取之处还是值得我们借鉴。