Swinging Physics: Potential And Kinetic Energy Working Together
动能与势能相互作用
动能是所有能看到的运动的能量，包括物体的，微粒的或质点集的运动等。
势能(Potential energy )是位置的函数，例如把一个重物举到一定的高度，当它下落时能够作功，所以它具有某种潜在的能量.
Sit on a swing, let someone push you, and away you go.
But what happens if the person who pushed you walks away, and you want to swing faster and higher. If you’ve ever been in the second grade, you know the solution to that. Just start pumping your legs–stretching them forward then drawing them up underneath you–and you can make yourself swing higher. Have you ever wondered why this is?
Potential Into Kinetic
Swings work by converting potential energy into kinetic energy, then kinetic energy back into potential energy, over and over again.
The kinetic energy is the fast part of swinging; it’s the speed you have as you rush back and forth.
Potential energy is the high part of swinging.
The higher you go on the swing, the more potential energy you have.
Speed and Swing
Even though you’re not moving at the very top of each swing, you can think of your height as your potential for speed. A physicist would say that your kinetic energy–that is, your speed–is “stored” as potential energy at the top of each swing.
More height is more speed, just waiting to happen.
How Do You Increase The Energy?
You can increase the energy of your swing in two separate ways.
If someone pushes you, that increases your kinetic energy.
By pumping your legs, you can increase your potential energy. By raising your legs at the top of each swing, you can raise the overall center of mass of your body, effectively raising the height of your swing.
Pump after pump, the energy you burn in your legs increases your swing’s potential energy. That extra height will add up, giving you a wilder swing ride.
译文：
坐上秋千，身后一人使劲一推，你便飞了出去，翱翔半空。
但要是再身后推你的人走开了，而你仍想秋千荡得更高更快，那该如何？这个问题，只要你上了二年级，就知道该怎么做。首先用以摇晃双腿，再向前伸展开来，最后将腿滑向身体之下，秋千就能荡得更高。但你是否想过这是什么原理？
势能转化为动能
秋千的工作原理是将势能转化为动能，然后又将动能再转化为势能，一遍遍的重复这个过程。
动能是秋千快的一部分能量，表现为来回运动时的速度。
势能存在于秋千荡的的高度之中。
秋千荡得越高，所获得的势能也就越大。
速度与秋千
即使在秋千的顶点你并没有运动，但你仍然可以将你的高度认为是潜在的速度。物理学家会告诉你，动能，也就是速度，储存在每次摆动顶端的势能里。
这就意味着，荡得越高，速度也就越快。
如何增加能量？
以下两种方式都可以增加摇摆的能量。
要是有人在身后推你，那将增加动能。
摇晃双腿的方式，增加的是势能。当双腿达到每次摇摆的顶部，身体重心也提高，这就有效的提升了秋千高度。
不断的摇晃，双腿产生的能量将增加势能。由此，秋千会荡得更高，更精彩。 |