差距
My daughter and son always have frictions. 我女儿和儿子总发生矛盾。
Friction causes a rolling ball to stop finally. 摩擦力使滚动的球最终停了下来。
Constant friction wore out the heels of my shoes. 不断的摩擦磨损了我的鞋跟。
Friction between two sticks can create a fire. 两个棍棒相互摩擦能起火。
In the absence of friction belted machinery would not be used. 没有摩擦力，皮带传动的机器就无法使用。
Matches are lighted by friction. 火柴由摩擦而生火。
