航天飞机重返地球大气层时因有摩擦力而减慢速度。
The force of friction slows the spacecraft down as it re-enters the earth's atmosphere.
磁悬浮不依赖于车轮在轨道上的摩擦力。
风向在城市里也会改变，因为建筑物增加了它们周围流动的空气的摩擦力。
Wind movements are also modified in cities because buildings increase the friction on air flowing around them.
这种毡制品只是为了消除与塑料产生太多的摩擦力，或者让它与外壳稍微分开。
This felt thing there is just to avoid too much friction from building up with the plastic or to keep it slightly separated from the case.
这种毡制品只是为了消除与塑料产生太多的摩擦力，或者让它与外壳稍微分开。
This felt thing there is just to avoid too much friction from building up with the plastic or to keep it slightly separated from the case.
它们的腿有点弯曲，脚尖上有小钩，提供足够的摩擦力，使它们能在湿滑的环境中活动。
The legs, which are slightly curved with tiny hooks on the tips of their feet to provide enough friction to enable movement in a slippery environment.
雨滴落在太阳能电池板上，然后滚落下来，此时它与电池板表面产生摩擦力，这种摩擦力可以转化为电能。
When a raindrop falls on the solar panel and then rolls down, it creates friction on the surface of the panel, which can then be turned into electricity.
因此，地质学家们想知道，断层内部的加压水袋是否会使板块之间的摩擦力减小，从而使板块彼此远离。
Geologists therefore wondered whether the friction between the plates was being reduced by pockets of pressurized water within the fault that push the plates away from each other.
这些属性包括物体的密度和摩擦力。
These attributes include the density of the object and the friction.
所以摩擦力做负功-，转化成热能。
绳子的这个方向的,摩擦力会翻转。
Those frictional forces for this rope to go in this direction will flip over.
我们知道在生活中，摩擦力抵消动能。
那么，究竟什么是摩擦力呢？
那摩擦力是多少，什么方向？
What will the friction be, how large, and in what direction?
若这棒上没有摩擦力，那么。
由此我得到，摩擦力的大小。
So I know what the frictional force is given by this result.
若我们利用摩擦力，就能得到稳定状态。
However, if we make use of the friction, then we can have a stable situation.
为什么摩擦力不起作用？
摩擦力会调整自身大小，使系统保持平衡。
The friction will adjust itself so that there is equilibrium if nothing is going.
改变的是，最大摩擦力。
摩擦力可以转移动能。
摩擦力一定抵消动能。
对比起木地板来说，冰面的摩擦力要小得多。
Compared to, say, a wooden floor, ice has much less friction.
假设现在没有摩擦力。
如果没有摩擦力，如果没有其他力，只有重力。
If there is no friction, if there are no other forces, only gravity.
我们发现了摩擦力。
所以这个是摩擦力。
摩擦力是怎么做的？
但是动量守恒，因为这里的，摩擦力都是内部的。
But momentum is conserved, because those frictional forces are all internal.
它未曾变过,如果没有空气阻力,或任何摩擦力。
That never changes if there is no air drag or air friction of any kind.
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