But for other materials, the kinetic friction can be lower than static friction.

没有静摩擦系数小于动摩擦系数的情况没有静摩擦系数小于动摩擦系数的情况。

So we don't know how much force it took to overcome static friction.

这里不知道 花了多大力克服静摩擦但我们知道。

But that's only half the picture. What about static friction?

但这只是事实的一半。 静摩擦呢？

When the two surfaces are not sliding  relative to one another the friction is static friction.

当两个表面不相对滑动时，摩擦就是静摩擦。

The force of static friction acts  upward from the wall on the book.

静摩擦力从墙壁向上作用于书本。

You also happen to know that the coefficient of static friction between the box and the ramp is 0.50.

你也意识到摩擦的程度 盒子和斜坡之间的静态是 0。50。

And the maximum force of static friction is just equal to the coefficient of static friction times the normal force.

最大静摩擦力为 静摩擦力乘以法向力的程度。

Also, for two surfaces, the coefficient of static friction is almost  always more than the coefficient of kinetic friction.

此外，对于两个表面，静摩擦系数几乎总是大于动摩擦系数。

And there's also STATIC friction — the force you had to overcome to get it moving in the first place.

有静摩擦... 你必须克服它才能移动。

Especially hypothetical ramps! So, let's say this ramp would allow for static friction, but not kinetic friction.

尤其是虚拟斜坡！所以，让我们说 这个坡度允许静摩擦，但。

And when glitter is just sitting on a surface, those Van der Waals' forces are also creating very weak static friction.

当闪光只是停留在一个表面上时，那些范德瓦尔斯力也会产生非常微弱的静摩擦。

The equation then is the force of static  friction is less than or equal to the coefficient of static friction times the force normal.

那么方程就是静摩擦力小于或等于静摩擦系数乘以法向力。

The bookcase still doesn't move, so static friction must still be pushing back with the same amount of force you are.

但是储物柜不动，所以它必须 静摩擦仍然以类似的力推动。

That means there is an equal but opposite force of static  friction which acts downward from the book on the wall.

这意味着存在一个大小相等但方向相反的静摩擦力，它从书本向下作用于墙壁。

What  happens then is that the force of static friction adjusts in an attempt to keep the two surfaces  from sliding relative to one another.

接下来会发生的是，静摩擦力进行调整，以防止两个表面相对滑动。

The maximum force of static friction which would prevent an object from sliding  on a surface is the force of static friction maximum equals the coefficient of static friction  times the force normal.

阻止物体在表面滑动的最大静摩擦力是静摩擦力最大值等于静摩擦系数乘以法向力。