雅思課外閱讀：雙語科學(xué)篇之摩擦力

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Friction摩擦力

When it becomes difficult for an object to freely move across a surface, friction may be the preventing force. Friction is the resistance of motion when an object rubs against and acts in the opposite direction of another object. When any two objects rub against each other they cause friction. Friction is a force that holds back another object from freely moving. A simple example are the brakes on an automobile.

當(dāng)物體難以在接觸面自由移動(dòng)時(shí)，摩擦力可能是其阻力。摩擦力是物體運(yùn)動(dòng)表面相互摩擦產(chǎn)生的，其方向與物體相對(duì)運(yùn)動(dòng)方向相反，阻力是物體磨擦?xí)r，產(chǎn)生的的反方向作用力。任何兩個(gè)物體相互摩擦，都會(huì)產(chǎn)生摩擦力。摩擦力是阻礙相互接觸的物體阻礙另一物體自由移動(dòng)的力。一個(gè)簡(jiǎn)單的例子是在汽車剎車。

Friction causes a second object to lose energy by slowing its motion. The energy does not disappear, but it changes from moving energy, which is called kinetic energy to heat energy or thermal energy. When a person rubs their hands together friction is generated and then it turns into heat. This is why cold hands become warm after rubbing them together. This is also called kinetic friction.

摩擦導(dǎo)致第二對(duì)象通過能量消耗從而減速。能量不會(huì)消失，但它從移動(dòng)的能量，也就是所謂的動(dòng)能轉(zhuǎn)熱能。當(dāng)一個(gè)人搓自己的雙手會(huì)產(chǎn)生摩擦力，然后將其轉(zhuǎn)變成熱量。這就是為什么冰冷的手相護(hù)揉搓后會(huì)變得溫暖。這也被稱為運(yùn)動(dòng)摩擦。

Friction can be found anywhere objects come into contact with each other. The brakes on a car causes friction between the brake pads and the wheels of the car, allowing the car to come to a stop. A person running on a sidewalk may stop quickly because of friction caused between the bottom of the shoes and the asphalt or concrete.

物體與其接觸面的摩擦力隨處可見。汽車剎車是因?yàn)閯x車踏板與汽車車輪之間的摩擦力讓車停下來。在人行道上跑的人能快速停止是源于鞋底和瀝青或混凝土之間的摩擦力。

However, other variables can lessen the effects of friction. For instance, if the sam e person running tried to stop on a water-covered sidewalk, friction would be less and the runner may not be able to stop as quickly, and in some cases may fall. This is similar to a car trying to stop on an ice-covered roadway. The friction is still there, but it is much less and may lead to accidents. Also, during rain, there is still friction between the brakes and the wheels, yet if the brakes are wet, the wheels would not be as much in contact with the ground. As a result, cars hydroplane when they go too fast on puddles of water.

然而，其他變量可以減少摩擦力的作用。例如，跑步者試圖在積水的人行道上停下來，但是因?yàn)槟Σ亮p小他可能很難立刻停下來，而且有時(shí)會(huì)摔倒。同樣，汽車試圖在冰雪覆蓋的道路上剎車。摩擦仍然存在，但要小得多，而且可能引起事故。又例如，下雨時(shí)，剎車踏板和車輪之間的摩擦力仍然存在，但如果離合器是濕的，車輪不會(huì)與地面接觸一樣多。其結(jié)果是，車子如果在水洼行駛速度過快如同水上飛機(jī)。

There are times when friction needs to be prevented so things will move more easily. Lubricants like grease and oil can help reduce friction between two objects. Engines and machines use grease and oil to reduce friction and wear so they can last much longer. Friction can also be reduced by using a ball or wheel on certain objects, which is called rolling friction. Changing the types of materials that come in contact with each other is another way of preventing friction. A good example is the use of roller skates on a concrete surface, ice skates on a lake covered with ice, or wearing rubber shoes on a wet sidewalk.

有些時(shí)候，需要減少摩擦使物體更容易移動(dòng)。像潤(rùn)滑油之類的油脂可以減少兩個(gè)物體之間的摩擦力。發(fā)動(dòng)機(jī)和機(jī)器使用潤(rùn)滑油以減少摩擦和磨損，使其能夠持續(xù)更長(zhǎng)的時(shí)間的工作。還可以在某些物體上使用球體或滑輪來減少摩擦，這被稱為滾動(dòng)摩擦。改變接觸材料是防止摩擦的另一種方式。一個(gè)很好的例子是在混凝土表面使用旱冰鞋，在結(jié)冰的湖面使用溜冰鞋，或者在濕滑的人行道使用膠鞋。

Besides dry friction as in some of the examples above, there is also static friction when objects are not moving such as the touching a metal surface and feeling a shock. When friction involves a fluid or air it is called fluid friction. The air resistance on an airplane, water resistance on a boat, and the slides at water parks are examples of fluid friction.

除了上文中提及的動(dòng)摩擦外，也有非運(yùn)動(dòng)物體的靜摩擦力，如觸摸金屬表面和撞擊。當(dāng)摩擦涉及流體或空氣，被稱為流體摩擦。飛機(jī)的空氣阻力，船的水的阻力，包括水上公園的滑梯都是流體摩擦的例子。

Finally, the two main factors that influence the total amount of friction include the roughness of the objects' surfaces and the force applied between the two objects. The measure of friction, its coefficient, is based on the roughness of the materials that come in contact with each other. For example, concrete on concrete has a very high coefficient of friction, and the Teflon surfaces of pots and pans have a low coefficient because it is a surface where most things do not stick.

最后，影響摩擦大小的兩個(gè)主要因素是接觸表面的粗糙度和作用在兩個(gè)對(duì)象之間的力。摩擦力，其系數(shù)是基于相護(hù)接觸的材料的粗糙度。例如，混凝土之間的摩擦系數(shù)非常高的系數(shù)，而鍋具的特氟隆表面的摩擦系數(shù)很低，因?yàn)榇蟛糠謻|西都不沾附其表面。

In summary, friction is the resistance of motion when an object rubs against and acts in the opposite direction of another object. There are four types of friction which includes kinetic friction, dry friction, rolling friction, static friction, and fluid friction. Common examples of friction are brakes on a car, ice skates, and wearing rubber shoes on a wet surface. Roughness and force of objects are factors of friction, and the coefficient of friction is a measure of how easily one object moves in relationship to another.

總之，摩擦力是當(dāng)物體摩擦另一對(duì)象而產(chǎn)生的相反方向的作用力。有四種類型的摩擦力，其包括動(dòng)摩擦，干摩擦，滾動(dòng)摩擦，靜摩擦和流體摩擦。摩擦常見的例子是在一個(gè)汽車剎車，溜冰鞋，在濕地穿膠鞋。摩擦因素是粗糙度和作用在對(duì)象上的力，摩擦系數(shù)用來評(píng)斷在一物體在另一物體上移動(dòng)的難易程度。

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