You know this if you swim, if you want to swim

你知道如果你游泳的话如果你想游泳
and just glide through the water, push off from the side

你可以只靠滑行从岸边一脚蹬开
and just glide, if you go like this

然后只需滑行如果你像这样滑行
you're not going to glide very far.

那你滑不了多远
If you put your hands in front of yourself or down at your side

如果把双手举在自己前方或者自己身后
and make your body more streamlined you're going to go a long ways,

使身体更趋流线型你就能走得很远
so streamlining helps.

因此流线型很有用
It turns out that there's a very simple relationship

你会发现对于球形或者接近球形的物体
between the drag force and the velocity

在向前运动时
that you move forward for objects

受到的拖曳力和速度之间存在着
that are spherical or roughly spherical.

非常简单的函数关系
I show that equation here.

我把方程显示在这了