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思考题 2.1)在伽利略之前,很多人认为力是维持物体运动的原因。他们说: “一个球在地平面上运动,若不继续施力于小球,则小球的速度将减慢,最后停止。”你如何分析这种看法? 2.2)有人说:“若加速度为零,第二定律就变成惯性定律,所以后者是前者的特例,惯性定律是可有可无的。”究竟惯性定律的必要性是什么? 2.3)既然牛顿三定律中的物体都是指质点而言,而质点又是忽略了形状大小的,那么强调“外”力,是不是无的放矢?对于质点,到底有没有“内力”问题?
Questions 2.1) Before Galileo, many people thought that force was the reason for maintaining the movement of objects. They said: “A ball moves on the ground level. If you don’t continue to force on the ball, then the speed of the ball will slow down and finally stop.” How do you analyze this view? 2.2) Someone said: "If the acceleration is Zero, the second law becomes the law of inertia, so the latter is a special case of the former, and the law of inertia is dispensable.” What is the necessity of the law of inertia? 2.3) Since the objects in Newton’s three laws all refer to In terms of the quality point, while the quality point ignores the size of the shape, then the emphasis on “external” force is not a target. For quality, in the end there is no “internal force” problem?