【英语时差8,16】跷跷板-上

Remember seesaws²? Those things were great. But there was often a problem. Suppose there’s a big kid on one side and a smaller kid on the other side. The seesaw¹ just stays in one position: big kid on the ground, smaller kid up in the air. No fun. After a few different tries, you probably realized that moving the big kid in toward the center made it possible to rock a little. Move the big kid even more and you can achieve balance. Now the seesaw works. What’s going on here? The answer is in the “center of mass.” The center of mass is a point somewhere along the plank³ that holds the two kids where their average weight falls. If you can get the center of mass to be over the pivot⁴ point, the seesaw will be balanced.

1 seesaw   

n.跷跷板

参考例句：

• Prices have gone up and down like a seesaw this year.今年的价格像跷跷板一样时涨时跌。
• The children are playing at seesaw.孩子们在玩跷跷板。

2 seesaws   

n.跷跷板，上下动( seesaw的名词复数 )v.使上下（来回）摇动( seesaw的第三人称单数 )；玩跷跷板，上下（来回）摇动

参考例句：

3 plank   

n.板条，木板，政策要点，政纲条目

参考例句：

• The plank was set against the wall.木板靠着墙壁。
• They intend to win the next election on the plank of developing trade.他们想以发展贸易的纲领来赢得下次选举。

4 pivot   

v.在枢轴上转动；装枢轴，枢轴；adj.枢轴的

参考例句：

• She is the central pivot of creation and represents the feminine aspect in all things.她是创造的中心枢轴，表现出万物的女性面貌。
• If a spring is present,the hand wheel will pivot on the spring.如果有弹簧，手轮的枢轴会装在弹簧上。