摇椅的原理似乎没有受到外力作用,为什么靠在座椅上的人的摇动可以使人和椅子一起摇动呢?座椅上的人可是与地面未接触的.如果把

诚然我们需要观测,但也可以通过近似方法和模型化处理来简化这一问题.
将你的摇椅底面近似为圆弧形,则摇椅的运动与单摆的运动完全类似.而单摆的运动在摆角较小的时候方可视为简谐运动（这也是一种近似处理的方法）,故如果摇椅摇摆的辐角较小时也可视为简谐运动.
细节可以加我详聊.

What is the purpose of life?Up to now I have no satisfactory answer yet for myself,but I can imagine I lie motionless in a rocking chair with the sunshine on my face when I become old and frail,recalling my life’s journey and the things past.What are the other things that can make me excited and what are the things that can make me remorsed?Will I show a composed smile or a mournful expression when the old and helpless me can’t do anything but wait in the rocking chair for my destined final moment?
Don’t leave any regret for yourself,since there are things that will never again arouse your passions in your remaining entire life if left undone.

想要使椅子摇摆,转动支撑点在地面,找最长的施力力臂点,应该是B才对

选b.
a是测承受重量了
c椅子就被推走了
d同上,方向还不对

滑梯：slide
摇椅：rocking chair
希望能够帮到你!

“我能想到最浪漫的事,就是和你一起慢慢变老,一路上收藏点点滴滴的欢笑,留到以后坐着摇椅慢慢聊.直到我们老得哪儿也去不了,你还依然把我当成手心里的宝...”翻译是"I can think the most romantic matter,is and you slowly agestogether,on a road collects the intravenous drip laughing heartily,will remain sits the rocking chainr to later slowly to chat Also wasold where until us not to be able to go,you also still regarded as mein the control the treasure..."