A:若物体某1秒内的平均速度是5m/s,则物体在这1s内的位移一定是5m
B:若物体在第1s末的速度是5m/s,则物体在第1s内的位移一定是5m
C:若物体在10s内的平均速度是5m/s,则物体在其中1s内的位移一定是5m
D:物体通过某位移的平均速度是5m/s,则物体在通过这段位移一半时的速度一定是2.5m/
若关于x的方程2-xx-5-m5-x=0有增根,则m的值是( )
阅读短文,判断正确还是错误。
A letter
Here is a letter from Jim to his friend in the USA
Dear Lily:
I am in China now. I go to school five days a week. The school and the food are good here. I have some Chinese friends. They are all very friendly to me. On Saturdays and Sundays we stay at home. In the afternoon we play games. My Chinese friends like English very much. They ask me to teach them English and they teach me Chinese. I like staying here.
Please write soon!
1840年至1901年短短几十年间,中国屡遭西方欺凌,被迫签订了一系列丧权辱国的不平等条约。其中严重阻碍中国民族工业发展的规定是( )
查阅资料得知:过氧化钠(Na2O2)是一种淡黄色固体,能与CO2、H2O发生反应:
2Na2O2+2CO2═2Na2CO3+O2
2Na2O2+2H2O═4NaOH+O2↑
请回答下列问题: