Newton discovered that any two objects in the universe attract each other, and that this force is proportional to their mass.

牛顿发现宇宙中任何两个物体都相互吸引，而且这股引力与它们的质量成比例。

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That is the analog of force divided by mass equals acceleration, which is d over dt of velocity.

这个类似于，力除以质量等于加速度，就是速度对t的导数。

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And so we know the force for a particular mass, and we know the area of the piston.

我们知道每个质量对应的力，也知道活塞的面积。

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Obama called for the task force after last month's mass shooting in Newtown in which 27 people were killed -- 20 of them elementary school children.

CNN: STORY HIGHLIGHTS

The commercial mass production of advanced electronic systems has made high-quality electronic devices exceedingly affordable, and slashed defense budgets force the U.S. military to look for cost savings wherever possible.

CENTERFORSECURITYPOLICY: Center For Security Policy

The bad force is an undulating, pullulating, filthy, dark mass, at the center of which a hell-mouth with dagger teeth and lips spews scalding yellow mist.

NEWYORKER: Green Lantern