文档介绍：第二章 动量守恒 质点动力学
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第一节 惯性定律
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§ 惯性定律
惯性定律 Law of Inertia
一个自由质点永远以恒定的速度运动,或者说,没有加速度。这就是说,一个自由质点可以沿直线作匀速运动,不然就是静止(速度为零)。这一定律也称牛顿第一定律。
惯性系 Inertial Frame
自由质点或系统,也就是说,它不受世界上其他物体的作用。
该参考系称为惯性参考系。
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惯性定律原为伽利略所发现,这个定律不能被直接用实验去证明。
原因:除非我们先有这个定律,否则我们实在无法回答什么是自由质点或系统,也就是说我们无法知道该质点或系统是否受其他物体的作用,这样也就无法选择作为描写相对运动的惯性参考系。
所以我们与其说惯性定律还不如说惯性原理。它实际上是一个假说,事实上这个假说反映了我们所处空间的“平直”性质。如果空间是“弯曲”的话,则自由质点将沿“弯曲”空间运动,不再是沿直线运动。
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The law of inertia can’t be proved by experiment.
Reason:
a free particle or system;
no interaction;
an inertial frame of reference;
Logical cycle appears
Galilean ideal experiment;
vo
v1 > vo
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The law of inertia can’t be proved by experiment.
Reason:
a free particle or system;
no interaction;
an inertial frame of reference;
Logical cycle appears
Galilean ideal experiment;
vo
v2 < v1
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The law of inertia can’t be proved by experiment.
Reason:
a free particle or system;
no interaction;
an inertial frame of reference;
Logical cycle appears
Galilean ideal experiment;
vo
v3 < v2
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The law of inertia can’t be proved by experiment.
Reason:
a free particle or system;
no interaction;
an inertial frame of reference;
Logical cycle appears
Galilean ideal experiment;
vo
v4 < v3
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The law of inertia can’t be proved by experiment.
Reason:
a free particle or system;
no interaction;
an inertial frame of reference;
Logical cycle appears
Galilean ideal experiment;
vo
v5 < v4
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The law of inertia can’t be proved by experiments.
Reason:
a free particle or system;
no interaction;
an inertial frame of reference;
Logical cycle appears
Galilean ideal experiment;
vo
v6 = vo
Therefore, the law of inertia is regard as the principle of inertia ( a sort of hypothesis ).
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