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(单词翻译)
There’s a simple way to figure out where the center of mass is. If the big kid is two times as heavy as the little kid, then their mutual1 center of mass will be two times closer to the big kid than to the little kid. Three times heavier and the center of mass will be three times closer. And so on. So the reason the heavy kid sits on the ground while the light kid is up in the air is that their mutual center of mass is on the heavy kid’s side of the pivot2. To make the seesaw3 work, the heavy kid must push that center of mass forward until it just touches the pivot. Then their average weight pushes right on the middle, letting the ends rock up and down.
收听单词发音
1
mutual
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| adj.相互的,彼此的;共同的,共有的 | |
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2
pivot
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| v.在枢轴上转动;装枢轴,枢轴;adj.枢轴的 | |
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3
seesaw
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| n.跷跷板 | |
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