The alternation of motion is ever proportional to the motive force impressed； and is made in the direction of the right line in which that force is impressed.
物體的加速度與所受的合外力成正比，與物體的質(zhì)量成反比。加速度的方向與合力的方向相同。
對(duì)幼兒來(lái)說(shuō)，媽媽的聲音是具有特殊意義的參照物。
地震是地質(zhì)事件，而不是氣象事件。
"The truth is not always beautiful, but the search for it is."