This is the moment of inertia.

这是转动惯量。

So we know the moment of inertia.

我们得到转动惯量。

What is the moment of inertia of that?

它的转动惯量是多少呢？

You can calculate the moment of inertia.

可以计算其转动惯量。

Well, the moment of inertia is a boring job.

计算转动惯量，是一个枯燥的活。

You get a totally different moment of inertia.

你会得到完全不同的转动惯量。

Almost all moment of inertia is in this system.

几乎所有这个系统中的转动惯量。

But least moment of inertia in transverse direction.

但最少转动惯量在横向方向。

We got three times the moment of inertia about the center.

也就是，关于中心处转动惯量的3倍。

All I have to know now is what is the moment of inertia about P.

我现在只需要知道，点p的转动惯量是多少。

So it is bMg divided by the moment of inertia about that point P.

也就是bMg除以,点P的转动惯量。

For the disk, all we have to do now is calculate the moment of inertia.

对圆盘，我们只需要，算出转动惯量。

Well, we will try to compute now the moment of inertia about this point.

我们要去计算关于这个点的转动惯量。

What is the moment of inertia for rotation of a rod about this axis?

关于这个轴的,旋转动动量是多少？

Conservation of angular momentum, moment of inertia, parallel axis theorem.

角动量守恒，惯量，平行轴原理。

OK, so moment of inertia about the z axis so, what's the distance to the z axis?

关于绕z轴的转动惯量,到z轴的距离是多少？

For the moment of inertia, we want the square of a distance to the axis of rotation.

至于转动惯量，要求的其实是到旋转轴距离的平方。

Needless to say, that the moment of inertia depends on what kind of object you have.

不用说，转动惯量取决于，你选择的物体。

How hard it is to spin something, on the other hand, is given by its moment of inertia.

旋转东西有多难，换着来讲的话，是跟转动惯量有关的。

But it's completely different, the moment of inertia, if you rotated it about this axis.

但它完全不同，转动惯量，如果将其绕这轴旋转。

If I know the moment of inertia, then I know how much rotational kinetic energy there is.

若知道转动惯量我就能知道，转动动能是多少。

It has to do, of course, with the moment of inertia, but again, it's independent of mass, radius and length.

肯定是，与时间惯量有关，再次，它与材料无关，还有半径和长度无关。

In rotation, force becomes torque, mass becomes moment of inertia, and acceleration becomes angular acceleration.

在旋转时，力变成力矩，质量变成转动惯量，加速度变成角加速度。

I will ask you for a moment of inertia for some weird line or something like that. OK, but these you should know.

我会让你们求一些，比较奇怪的曲线的转动惯量，这些你们都应该知道。

We have the mass of the sun, we have the radius of the sun so you can calculate the moment of inertia of the sun.

我们知道太阳的质量，太阳的半径,所以可以计算出,太阳的惯性是多少。

For example, the moment of inertia about the z-axis is dV the triple integral of x squared plus y squared density dV.

例如，关于z轴的转动惯量,是∫∫∫δ

I mean, there are some spokes here, but let's assume that everything is here, so then the moment of inertia is MR squared.

我是说，有一些偏差，但是假设每件事都在这，所以时间惯量是MR的平方。

Torque divided by moment of inertia is what will cause the angular acceleration, namely the derivative of angular velocity.

扭矩除以转动惯量,就会引起角加速度，也就是角速度的导数。