,势能是多少。
那么势能呢？
现在是势能。
Of the gravitational potential energy...
重力势能的关系。
This is the gravitational potential energy.
这是重力势能。
There is potential energy in that spring.
弹簧中储存了能量。
And how about potential energy? It is not bound.
那么什么是势能，答案不是一定的。
That's the potential energy from the spring.
那是弹簧储存的能量。
The force will drive it to lower potential energy.
势能减小的方向，如果我们知道这个力。
Mhy You see? Mgy is gravitational potential energy.
你们看，是重力势能。
Notice the gravitational potential energy goes down.
注意，重力势能，是减小的。
And that's potential energy that goes into the spring.
这是存进弹簧的能量。
Calories can be defined as potential energy for the body.
卡路里对于身体来说是一种潜在的能量。
Notice that the gravitational potential energy increases.
注意，这里，重力势能是增加的。
That means the sum of potential energy and kinetic energy.
总功指的是势能,和动能的总和。
That is the potential energy at c, which reaches a maximum.
这是点c的势能，在此达到最大值。
And this is what we call the potential energy of the spring.
弹力势能，这是势能。
The sum of kinetic energy and potential energy doesn't change.
动能和势能，总和没有改变。
So this is the kinetic energy and this is the potential energy.
因此这是动能，这是势能。
The spontaneous change lowers the potential energy in that case.
在这个例子中,自发变化减小了势能。
In fact, what will happen is it will go to a lower potential energy.
事实上，它会，朝着低势能方向移动。
We call mgy... we give that a name, "gravitational potential energy."
我们把mgy叫做。,给它一个名字，重力势能
You see, that is the term of the potential energy that you have there.
你们看，这是，我们已经得到的，势能的等式。
The attractive energy is just the potential energy, Coulombic potential.
引力能就是电势能，库伦电势。
It is a free electron so there is no potential energy to be accounted for.
对于自由电子，因此没有什么势能。
In fact, anything we eat is considered to be potential energy for our body.
事实上我们吃的任何东西都是身体的潜在能量。
I could have chosen my zero point of potential energy anywhere I please.
作为重力为0的点，我可以选择这里。
Let me first give you the formal definition of gravitational potential energy.
我先给你一个对于，重力势能的形式定义。
Why collect all this information if most of this potential energy will never be tapped?
如果这些潜在能源永远不能被利用那么收集这些信息还有什么意义？
That was the potential energy of the spring that was converted into kinetic energy.
这是弹簧储存的能量，它转化为动能。
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