动量被认为是“守恒的”，也就是说，动量一旦被建立，就一定会转移到其他地方。
Momentum is said to be "conserved", that is, once you build it up, it has to go somewhere.
例如，无论一个舞者多么想要跳离地板，然后开始旋转，角动量守恒定律绝对阻止这样的动作。
For example, no matter how much a dancer wishes to leap off the floor and then start turning, the law of conservation of angular momentum absolutely prevents such a movement.
在皮亚杰之前，没有人注意到守恒。
动量守恒，这就叫作动量守恒。
Momentum is conserved, and that's called the conservation of momentum.
动量守恒定律告诉你,碰撞后速度是多少。
So the conservation of momentum tells you what the speed is after the collision.
角动量，在点Q守恒，也只有在点Q守恒。
Angular momentum is conserved about this point Q, but only about that point Q.
它讲的是能量的守恒。
你看，这正是，验证动量守恒的方法。
So, you see, that's exactly how you can demonstrate the conservation of momentum.
下一个，动量守恒。
但动量却守恒。
也就在反应期间,我有个合理假设，动量是守恒的。
It's just during the impact I claim that to a reasonable approximation, momentum will have to be conserved.
这是我们第一次，在这种系统里使用，角动量守恒定律。
Now we're going to apply for the first time in systems like this, the conservation of angular momentum.
这一原理，也即能量守恒，是物理学中最宝贵的定律之一。
This principle, called conservation of energy, is one of our most cherished laws of physics.
能量守恒是科学家已发现的关于宇宙的最基本的规律。
Conservation of energy may be the most basic rule that scientists have yet discovered concerning the universe.
势能的改变量，将会转化成动能的改变量，这就是能量守恒定律。
The change in potential energy is going to be the change in kinetic energy You have conservation of energy principles.
结果显示质点跟踪法不仅耗散更低，而且守恒性也更好。
The result shows that the Particle-tracing Method is not only less diffusive , but also more conservative.
其结果，其中一些方程非常眼熟，比如动量守恒定律和牛顿第二定律。
Turns out, some of these equations were very familiar: the law of conservation of momentum, and Newton's second law of motion.
如果违反能量守恒的持续时间不太长，那么自然界并不反对这种违反。
Nature has no objection to a violation of energy conservation, provided (that) the violation does not last too long.
研究人员计算出这会怎样影响整个地球自转速度，这有助于保持角动量守恒。
The researchers calculated how this would affect the rotation rate of the whole planet, which would compensate to conserve angular momentum.
如果没有这种数量守恒约束，glpsol就会将下面的错误打印到stdout上。
Without the mass conservation constraints, glpsol prints this error to stdout like so.
由于物理定律规定能量守恒，其它恒星将获得同等巨大能量的推动，以惊人的速度飞走。
Since the laws of physics dictate that energy be conserved, the other star would gain an equally large energy boost, flying away at tremendous speed.
因此呢，当(我们做的)实验违背了能量守恒定律的时候，我们有充分的理由来质疑它。
So when an experiment seems to violate the law of energy conservation, we are rightfully suspicious.
所有这些各种各样的损耗，尽管它们数量很大，却一点也不违反能量守恒定律。
All these various losses great as they are do not in any way contradict the law of conservation of energy.
必须记住，动量守恒甚至对于非弹性碰撞也是成立的，尽管这时动能已不守恒。
It is important to realize that momentum conservation applies even to inelastic collisions, in which the kinetic energy is not conserved.
物理学一条基本定律认为动量守恒，也就是说，除非外力进入系统，否则总动量一定保持不变。
A fundamental law of physics holds that momentum is always conserved, meaning that unless some outside force enters a system, its total momentum must stay constant.
因此，说能量守恒，就等同于说现在的物理定律与从前的物理定律相同，到了未来也不会改变。
So, saying that energy is conserved is as solid as saying that the laws of physics are the same now as they were in the past and will be in the future.
力学系统的对称性与精确不变量（守恒量）在力学、物理学中具有非常重要的意义。
The studies on symmetries and exact invariants (conserved quantities) play a very important role in mechanics and physics.
文章论述与实例相结合，灵活运用质量守恒定律，解答具有一定难度的初中化学习题。
Combining discussion with true examples, this essay solves certain chemical exercises of Junior Middle School through the law of mass conservation flexibly.
下一阶段，具体运算阶段，七到十二岁，儿童可以解决守恒问题，但儿童的抽象推理能力仍然有限。
The next phase, concrete operations, from seven to twelve, you can solve the conservation problem, but still you're limited to the extent you're capable of abstract reasoning.
下一阶段，具体运算阶段，七到十二岁，儿童可以解决守恒问题，但儿童的抽象推理能力仍然有限。
The next phase, concrete operations, from seven to twelve, you can solve the conservation problem, but still you're limited to the extent you're capable of abstract reasoning.
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