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.
有些时候,需要减少摩擦使物体更容易移动。像润滑油之类的油脂可以减少两个物体之间的摩擦力。发动机和机器使用润滑油以减少摩擦和磨损,使其能够持续更长的时间的工作。还可以在某些物体上使用球体或滑轮来减少摩擦,这被称为滚动摩擦。改变接触材料是防止摩擦的另一种方式。一个很好的例子是在混凝土表面使用旱冰鞋,在结冰的湖面使用溜冰鞋,或者在湿滑的人行道使用胶鞋。
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.
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2020-09-15
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