So you have this counteracting normal force.

这个力，也就是平行於斜面的这个地心引力的分力。

And this is the normal force.

这个力，也就是平行於斜面的这个地心引力的分力。

So this is the normal force.

所以这是支持力。

So the normal force that I have to apply is 12.25 times the mass.

的支持力是12.25乘以质量所以这是我施加的力 乘以质量。

So you have the normal force is equal to 9.8 times the mass divided by 0.8.

所以支持力等於9.8乘以质量9.8除以0.8等於12.25 所以我施加。

We're sitting on the ground in the vertical direction, normal force counteracting the force of gravity.

现在考虑更多的例子。

So the ground is providing an upwards force or normal force in this situation.

现在考虑更多的例子。

The ground is providing a normal force, I'll do it in green.

现在考虑更多的例子。

And I have the normal force. The rock is being supported by the ground 5 N upwards.

现在考虑更多的例子。

5 N normal force of the ground supporting the rock.

现在考虑更多的例子。

Similarly, the normal force is an external force but it's exactly cancelled by the gravitational force.

同样， 法向力是一种外力，但它恰好被引力抵消了。

And there's still a normal force , the ground supporting the rock of 5 N upwards.

现在考虑更多的例子。

People think that the normal force is always mg, we saw that that's not true.

人们认为法向力总是 mg，我们看到事实并非如此。

It's only the normal force on this five kilogram mass that's contributing to this force of friction here.

只有作用在这个 5 千克重物上的法向力才对此处的摩擦力产生影响。

The force of gravity is being balanced by the normal force of the ground.

现在考虑更多的例子。

I should say the magnitude of the normal force.

这可以通过实验来求。

People also think the normal force is always up, but it's not.

人们还认为法向力总是向上，但事实并非如此。

We will not draw the normal force up.

我们不会绘制法向力。

But if you put it on a ramp, then the normal force is pointing perpendicular to the ramp.

但是如果我们把它放在斜坡上，那么力 自然倾向于垂直于斜坡。

It just so happens that this horizontal force depends on a vertical force, which is the normal force.

碰巧这个水平力取决于垂直力，这是法向力。