那个圆锥头表示正方向。
这个方向，是y的正方向。
改变了正方向，这是有理由的-，充足的理由。
The reason why I now switch directions - and call this plus — as well as this — is a good reason for it.
所以当曲面正方向如此时，结果是正的。
当然这是因为没给出抛物面的的正方向。
Of course, I didn't tell you which way I am orienting my paraboloid.
因为它是可逆的，所以可以正方向运行。
And now since it's reversible, we can run it forward or backward.
纵坐标的正方向，横坐标的中间区域。
我需要选择一个正方向。
对于物体二，以向下为正方向,有m2g-T等于。
I call this the plus direction, so for object number two m2a I have m2 g minus T equals m2 times a.
我把这个选为正方向。
还有q 2一撇，在这个例子中，我们把箭头朝正方向。
And we're going to have q2 prime, and we're going to draw the arrows in the positive direction in these cases.
下面将系统,向上加速-,规定这个是正方向。
Now let's accelerate this system upwards a with an acceleration a-- and I call this plus.
失败能帮助自己修正方向并且提供丰富的学习机会。
Mistakes are a form of course correction and offer huge learning opportunities, says Hassler.
对于这个定理，我选择的方向是,指向外的正方向。
The orientation that will work for this theorem is choosing the normal vector to point outwards.
因此加速度必然,是在x正方向-,这里是正好，必然如此。
Therefore the acceleration since I call - that the "plus x direction"-- that was my plus sign-- must come out plus.
如果沿着C走，我应该说沿着C的正方向走，就是我确定了C的定向。
If I walk along c, I should say in the positive direction, in the direction that I have chosen to Orient c.
理性能帮人把正方向不犯错误却会束缚手脚让人丧失机会。
Ration can lead people to persuit right point avoiding erros , there is not necessarily the case, however , trapping us to lose some chances.
加速度在这个方向上，我规定它为正方向“，这个为负方向。”
Acceleration is in this direction and I will call this "plus" and I will call this "minus."
因而箭头是从高电位指向低电位，并且与假定的电流正方向一致。
Thus the arrow points from high to low potential and in the direction of assumed current flow.
根据以前所有的例子，一旦这种模式的火车开动了，就很难改正方向。
In every prior case, once the train gets rolling, it has been very difficult to correct course.
它进行，只要在交流电压保持在正方向和电流高于其保持电流电平。
It conducts as long as the AC voltage remains in positive direction and the current is above its holding current level.
这样，就算着陆时飞机没有对准跑道，飞行员还是有办法修正方向的。
As a result, a pilot has more latitude to land safely even when he is not aligned with the runway.
因此我决定，在此处改变正方向，加速度方向就始终为正了，符号变了。
So the moment that I decide to define this the plus direction will also come out to be the same sign as this one so I flip the signs there.
,在y的负方向,那么也有一个常力,在y的正方向,这两个力互相抵消。
in the minus y direction and there is a normal force in the plus y direction and these two exactly cancel each other.
为了方便，正方向设为向下，方向如何取并不打紧，还有重力mg的-，作用。
And just for my convenience I call this now the plus direction just for my convenience — it doesn't really matter So now we have here mg — that is gravity acting upon you.
随着不锈钢表面的钝化、电位朝正方向移动，然后回复到通常的电偶腐蚀行为。
When the stainless steel became passivated, the potential of the couple shifted towards positive and then resumed normal galvanic corrosion condition.
当施加到阳极的交流电压上升，在正方向上，电流流经可控硅的栅极-阴极部分。
When the AC voltage applied to the anode rises in the positive direction, current flows through the gate-cathode section of the SCR.
我把向黑板里面的，这个力矩，认为是正方向，而向黑板之外的，那个力矩，我认为是负方向。
And I call the torque that is in the blackboard, I call that my positive direction, and the torque that is out of the blackboard, I give that a negative direction.
这里我们并没有曲面定向的概念，能做的就是，从两个法向量中选出一个作为正方向。
Here we don't have a notion of orienting the surface other than by precisely choosing one of the two possible normal vectors.
这里我们并没有曲面定向的概念，能做的就是，从两个法向量中选出一个作为正方向。
Here we don't have a notion of orienting the surface other than by precisely choosing one of the two possible normal vectors.
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