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.

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。

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The general low level of friction on ice allows a skater to glide along the surface smoothly without friction stopping the motion as soon as it's begun.

冰面上摩擦力通常较低，这使得滑冰选手一俟启动，就能不受摩擦力牵绊，顺畅滑翔冰面。

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If indeed the friction coefficient is independent of surface area, then when I tilt them they should start to slide roughly at the same Angle.

若摩擦系数真的，与接触面积没有关系，那么两者下滑时的角度，应该基本相当。

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What's more, a machine-made surface produces the wrong kind of friction: to do its job precisely, the plate's surface needs minute scorings, of only a few microns each, where machine oil can reside.

CNN: ASIANOW - TIME Asia | GizmoLand! | Man Beats Machine

But on a high friction surface like clay, the ball will grip more and change the trajectory of the ball quite significantly.

BBC: SPORT | Tennis | Rules and Equipment | On the rebound

The crushed-brick mixture that constitutes the base of a clay court produces a the highest bounce and most friction of the three surfaces, meaning they have the lowest CPR of all three surface types and are considered as the "slowest".

CNN: Tennis interactive: Why clay is so different