题目详情

阅读下列案例,并回答问题。

[案例]

  下面是一节物理课“摩擦力”的教学实录(摘要):

  一、新课导入

  师:这节课我给大家带来几条小泥鳅,长得虽然不好看但却很有趣。哪个同学能帮我抓出来呢?(三名同学都没有抓住)

  师:想一想,为什么泥鳅这么难抓啊?(同学们议论纷纷)

(接着教师又拿出钉鞋、跑鞋、平底鞋、棉鞋、溜冰鞋各一双)

  师:如果老师要参加100米赛跑,你会选哪一双鞋呢?如果我要溜冰你又会帮我如何选择呢?为什么要做这样的选择?(同学们又热烈讨论)

  师:大家看个小实验(课件演示):让毛刷从平面上刷过,你观察到什么?

  众生:毛刷向右刷过刷毛向左倾斜,说明摩擦力的方向与相对运动的方向相反。

  师小结:一个物体在另一个物体表面上滑动时所受到的阻碍物体相对运动的力,叫摩擦力。

  二、深化学习

  师:摩擦力的大小可能与哪几个因素有关呢?请大家用手正向和反向摸狗尾巴草,看有什么不同感受?再看播放的视频,然后讨论。(视频显示:在光滑的和在粗糙的地面上拉着大小及重量不同的物体,弹簧秤测试出各自的摩擦力。)

  众生:(广泛争论后取得结论)摩擦力的大小跟压力的大小、接触面的粗糙程度有关。在接触面不变的情况下,压力越大,摩擦力越大;在压力不变的情况下,接触面越粗糙,摩擦力越大。

  三、知识应用

  师:摩擦力对我们的生活是有益的还是有害的?我们如何利用或克服摩擦力?

  众生:人走路时不打滑多亏了摩擦力;下雪天,路滑,撒些炉灰增加摩擦力防滑;拿起一个杯子,靠的就是手与杯子之间的摩擦力……机器零件之间的摩擦是有害的,加润滑油可以减少摩擦力……

  四、布置作业

请发现生活中与摩擦力有关的问题,提出利用或克服摩擦力的措施和建议。

[问题]请运用教学过程中学生掌握知识的基本阶段理论,对该物理教师的教学进行分析。

正确答案及解析

正确答案
解析

该教师较好地遵循了教学过程中学生认识的特殊性规律,依据学生掌握知识需要经过的四个阶段,取得了较好的效果。

  (1)感知阶段:教师通过让学生抓小泥鳅,又通过比较钉鞋、跑鞋、平底鞋、棉鞋、溜冰鞋的特点选择合适的鞋,还通过实际体验抓摸狗尾巴草,观看多媒体演示,使学生对什么是摩擦力、摩擦力的大小及其影响因素有了初步的感性认识。

  (2)理解阶段:教师通过讲授和演示进一步引导学生总结出摩擦力的定义以及影响因素,使学生在理解教材的基础上,进一步掌握了摩擦力的原理。

  (3)巩固阶段:教师进一步引导学生讨论生活中摩擦力的利与弊,使学生懂得如何运用所学知识为生活服务,并以归纳和总结的方式,巩固了所学内容。

  (4)运用阶段:教师通过布置作业,要求学生结合所学有关知识,解决实际生活中的问题。

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Salt is added to food partly to extend shelf-life.but more often it’s dropped in to make up for theflavor lost in the manufacturing process.This is especially true of ready meals and highly processedfoods.but it’s also true of such basic food as biscuits,soups,and even bread.Much mass—producedbread,for instance.contains so much salt.half a gram for every hundred grams of bread--that it’sofficiallv classified bv the UK government as high——salt food.Salt has to be added to the bread becausefast Droduetion cuts down the time for the flavor to develop.Without added salt,the bread would tastelike paper.?

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Heahh care experts have long drawn attention to the problems of eating too much sah.There isstrong evidence that a diet high in salt can lead to raised blood pressure.Since high blood pressure is amajor factor in heart disease.it makes sense to cut down on the salt people eat.?

In the past,food contained very little salt,and people added it to their food at the table.Very fewpeople ?add ?salt this ?way ?nowadays.However,the ?salt ?content ?of processed ?foods has ?gone ?updramatically.It’s now estimated that over three.quarters of the salt in the average diet comes fromprocessed foods,eaten without our being aware of it.?

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In the UK,the government has launched a campaign to cut down on the salt people eat.The UK Food Standards Agency argues that nearly half of the UK’s population eat too much salt—9.5 9 a day onaverage.Its aim is to bring down the average t0 69 a day.The idea is to cut the salt content in 85 keyfood categories such as bread.meat.and cakes.?

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Heahh care experts have long drawn attention to the problems of eating too much sah.There isstrong evidence that a diet high in salt can lead to raised blood pressure.Since high blood pressure is amajor factor in heart disease.it makes sense to cut down on the salt people eat.?

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