With some degree of confidence, I'm working with a reliable spring and then I will get the mass of the elephant.

这时我就对弹簧有信心了,我用的是一个可靠的弹簧,我能测出大象的质量

耶鲁公开课 - 基础物理课程节选

We know now with the same spring, by this comparison, we will find all objects now can be attributed a mass.

我们现在知道利用相同的弹簧,采用这种比较的方法,就会发现,所有物体都有确定的质量

耶鲁公开课 - 基础物理课程节选

You hook one end of the spring to a wall and you pull it from rest by some amount and you attach the one kilogram mass to it.

你把弹簧的一端固定在墙上,然后拉伸一段距离,接着你把 1 千克物体固定在上面

耶鲁公开课 - 基础物理课程节选

This is the force exerted by the spring on the mass.

这是弹簧对物体的作用力

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For example, how do I know that when I pull the spring the first time for the mass, it exerted the same force when I pulled the spring the second time for the elephant?

例如 怎样才能知道,第一次连着物体拉弹簧时,产生的力和,第二次连着大象拉弹簧时产生的力是相等的呢

耶鲁公开课 - 基础物理课程节选

A mass is attached to a spring.

一个物体与弹簧相连

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You cannot say to me, "Take a force, due to a spring, and see what force it applies and divide by the acceleration and get the mass, " because we haven't defined force, either.

你不能说,"给弹簧施加一个力,看看它能提供多大的力,然后除以加速度,得到质量",因为我们还没给力下一个定义

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Then, I bring the elephant and I pull the spring by the same amount and I find the acceleration of the elephant and the denominator is obviously the mass of the elephant.

然后我再找来大象,用相同的力去拉弹簧,大象就具有了加速度,很明显,分母就是大象的质量

耶鲁公开课 - 基础物理课程节选