如图所示，小球密度小于烧杯中的密度，球固定在弹簧上，弹簧下端固定在杯底。当装置静止时，弹簧伸长△x,当装置自由下落过程中弹簧的伸长将（
- Bill, can I get you anything to drink? - ______ .A. You are welcome. B. No problem.C. I wouldn’t mind a coffee. D. It doesn’t matter
以NA代表阿伏加德罗常数，关于热化学方程式： CH4(g)+2O2(g)=CO2(g)+2H2O(l)△H=-890kJ/mol，下列说法中正确的是 A．有4NA个电子转移时，放出890 kJ的能量 B．有NA
阅读下面两首诗，回答问题。（6 分） 夕阳楼 李商隐 花明柳暗绕天愁，上尽重城更上楼。欲问孤鸿向何处？不知身世自悠悠。 ①“花明柳暗绕天愁”
地球赤道上有一物体随地球的自转而做圆周运动，所受的向心力为F1，向心加速度为a1,线速度为v1,角速度为ω1;绕地球表面附近做圆周运动的人造卫星受
he had never worked so hard in his life. A. It seemed to me that B. He seemed as if C. There seemed that D. He seemed like
一个质量是0.3kg的水壶，装满水的总质量是0.8kg，装满另一种液体时的总质量是0.7kg，则水壶的容积是_________m3，这种液体的密度是_______kg/m3。
If you want to be successful, you must be ________ about the chance of overcoming the failure. A. optimistic B. skeptical C. previous
