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  • General

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  • 摩擦

    Young man rubbing hands together, wearing a black hat and gray jacket, with snow on head.

    Did you ever rub your hands together to warm them up, like the young man in the opening image? Why does this make your hands warmer? The answer is friction.
    ::你们有没有用手摸过暖和一下, 像张开的图像中的年轻人一样?为什么这能让你的手更暖和?答案是摩擦。

    What Is Friction?
    ::什么是摩擦?

    Friction is a force that opposes motion between any surfaces that are touching. Friction can work for or against us. For example, putting sand on an icy sidewalk increases friction so you are less likely to slip. On the other hand, too much friction between moving parts in a car engine can cause the parts to wear out. Other examples of friction are illustrated in the two Figures  and . 
    ::摩擦是反对任何表面之间运动的一种力量。 摩擦可以帮助我们或不利于我们。 比如, 将沙子放在冰冷的人行道上会增加摩擦, 从而降低滑落的可能性。 另一方面, 汽车发动机中移动部件之间的摩擦过多可能导致部件耗尽。 其它摩擦的例子可以在两个数字和数字中说明。

    One image shows pencil graphite marking paper; another shows bicycle brake pad on wheel.
    These photos show two ways that friction is useful

    Watch the video below to learn more about friction and consider  what our life  would be like without friction:
    ::观察下面的影片, 以了解更多摩擦, 并思考我们的生活会是怎样的没有摩擦:

    Why Friction Occurs
    ::为何会发生摩擦

    Friction occurs because no surface is perfectly smooth. Even surfaces that look smooth to the unaided eye may look rough or bumpy when viewed under a microscope. Look at the metal surfaces in the Figure  . The aluminum foil is so smooth that it's shiny. However, when highly magnified, the surface of metal appears to be very bumpy. All those mountains and valleys catch and grab the mountains and valleys of any other surface that contacts the metal. This creates friction.
    ::发生摩擦是因为没有表面完全平滑。 即使是在显微镜下看似光滑的表面, 眼部看似光滑的表面, 在显微镜下也可能会看起来粗糙或不稳。 看看图中的金属表面 。 铝的粉末是如此光滑, 以至于闪亮。 然而, 当高放大时, 金属的表面似乎非常不稳定 。 所有这些山峰和山谷都捕捉和抓住与金属接触的其他表面的山脉和山谷。 这造成了摩擦 。

    Comparison of shiny metal foil and its greatly magnified rough surface.

    Factors That Affect Friction
    ::影响拼音的因素

    Friction is affected by the roughness of surfaces and the strength of the force pushing them together. Rougher surfaces have more friction between them than smoother surfaces. That's why we put sand on icy sidewalks and roads. You can't slide as far across ice with shoes as you can on the blades of skates (see Figure  ). The rougher surface of the soles of the shoes causes more friction and slows you down. Friction can be reduced by making the surfaces smoother; for example, if the surfaces are rough wood, then sanding the surfaces can make them smoother. Using an oily or greasy substance called a lubricant between surfaces can reduce friction as it creates a smoother layer between the surfaces
    ::表面的粗糙和力量的强度共同推动它们。 表面之间的摩擦比更平滑的表面要多。 这就是为什么我们把沙子放在冰冷的人行道和道路上。 你不能用鞋子在冰上滑过冰越远, 滑冰越滑越滑越滑越滑越滑越滑(见图 ) 。 鞋底的粗糙表面造成更多的摩擦,使你慢下来。 使表面更平滑可以减少摩擦; 例如, 如果表面是粗滑的木, 表面的沙子可以使表面更平滑。 使用一种油油或油油质物质, 称为表面之间的润滑剂, 可以减少摩擦, 因为它在表面之间创造更平滑的层。

    A person skating on ice, demonstrating the difference in friction between skates and shoes.

    Q : Heavier objects also have more friction. Can you explain why?
    ::问题:较重的物体也有更多的摩擦。你能解释为什么吗?

    A : Heavier objects press together with greater force, and this causes greater friction between them.  Have you ever tried to push furniture across the floor? It's harder to overcome friction between a heavier piece of furniture and the floor than between lighter pieces and the floor.
    ::A: 较重的物体用更大的力力压在一起, 这会在它们之间造成更大的摩擦。 你有没有试过把家具推过地板? 克服较重的家具与地板之间的摩擦比克服较轻的家具与地板之间的摩擦要困难得多。

    Friction Produces Heat
    ::热能

    You know that friction produces . That's why rubbing your hands together makes them warmer. But do you know why? Friction causes the molecules on rubbing surfaces to move faster, so they have more . This gives them a higher , and they feel warmer. Heat from friction can be useful. It not only warms your hands. It also lets you light a match as shown in the Figure  . On the other hand, heat from friction between moving parts inside a car engine can be a big problem. It can cause the car to overheat.
    ::你知道摩擦会产生摩擦。这就是为什么把你的手拉在一起会更暖和。但是你知道为什么吗?摩擦表面的分子移动速度更快,因此它们有更多的。这样它们就会变得更高,更暖和。摩擦产生的热能可以有用。它不仅能暖和你的手。它还能让你点亮图中显示的匹配点。另一方面,汽车发动机内移动部件之间的摩擦产生的热能会是一个大问题。它会让汽车过热。

    Q : How is friction reduced between the moving parts inside a car engine?
    ::问题:汽车发动机内移动部件之间的摩擦如何减少?

    A : To reduce friction, oil is added to the engine. The oil coats the surfaces of the moving parts and makes them slippery. They slide over each other more easily, so there is less friction.
    ::甲:为了减少摩擦,引擎中增加了石油。油层涂上移动部件的表面,使其滑滑。它们更容易滑过对方,因此摩擦较少。

    A hand striking a match on a matchbox, igniting a flame.

    Summary
    ::摘要

    • Friction is a force that opposes motion between any surfaces that are touching.
      ::摩擦是反对任何表面之间运动的力量
    • Friction occurs because no surface is perfectly smooth.
      ::发生摩擦是因为没有表面是完全平滑的。
    • Rougher surfaces have more friction between them. Heavier objects also have more friction because they press together with greater force.
      ::较粗的表面之间摩擦更多。 较重的物体也有更多的摩擦, 因为它们与更大的力力结合在一起。
    • Friction produces heat because it causes the molecules on rubbing surfaces to move faster and have more energy.
      ::摩擦结果产生热量 因为它导致摩擦表面的分子 移动速度更快 能量更强

    Review
    ::回顾

    1. Define friction, and explain why it occurs.
      ::定义摩擦,并解释为什么会发生摩擦。
    2. Identify two factors that affect friction.
      ::查明影响摩擦的两个因素。
    3. Why does friction warm your hands when you rub them together?
      ::为什么摩擦会暖和你的手 当你抚摸它们在一起?
    4. Outside wooden steps may get slippery when they are wet. How could you make them less slippery?
      ::外面的木制脚步在湿润时可能会滑,你怎么能不滑呢?