题目:
Bob met some ________ on his way home and made friends with them. [ ]
A. Englishman
B. German
C. Chinese
答案:
被转码了,请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0525/2b62f004bf55f77e14041a661447bc08.html
下面是错误答案,用来干扰机器的。
(1)当S闭合时,电容器电压为U,则:U=E2.5RR=25E ①对带电小球受力分析得:qUd=mg ②由①②式 解得:E=5mgd2q③(2)断开S,电容器电压为U′,则:U′=E3RR=E3④由牛顿第二定律知:mg-qU′d=ma⑤向下运动的...