Where is the center of mass of this system?
这系统的重心何在？
And the center of mass of this eraser is somewhere in the middle.
这个橡皮重心在中间的某一点。
So here is the center of mass of that ladder, right in the middle.
这里是梯子的重心，在正中央。
But one that you might have seen in physics, we care about maybe where is the center of mass of a given object?
但你们可能也在物理学中见过了，就是求一个给定物体的重心？
In particular, we have seen the notion of center of mass.
特别地，我们学过质心的概念。
And this, now, is the position vector of the center of mass.
现在，这里是，物体的矢量中心。
And now comes another unique property of the center of mass.
它还有一个特性，质量重心的特性。
How do we calculate the velocity of the center of mass?
我们怎样计算，重心速度呢？
So the center of mass will always find itself below the point of suspension.
所以物体的重心，经常处于悬挂点之下。
The center of mass is basically a point that you would say is right in the middle of the object.
理论上，重心就是,恰好处在物体中心的点。
So this is the velocity of the center of mass.
这就是重心速度。
because it's a unit disk. And, the center of mass is the center of a disk.
因为它是一个单位圆盘，这部分的中心就是圆盘的中心。
If I look at the definition of the center of mass, it's the average value of x.
由质心的定义可知，它就是x的平均值。
The center of mass is lower, around half of the machine height.
该中心的质量较低，大约一半的机器的高度。
For this to be effective, it is necessary to keep the center of mass in normal flight directly below the center of pressure.
对，这是有效的，有必要保持中心的大规模正常飞行直接低于中心的压力。
A center of symmetry must coincide with the center of mass.
对称中心必须与质量中心重合。
A center of symmetry must coincide with the center of mass.
对称中心必须与质量中心重合。
应用推荐