质量为m的小金属球可视为质点,用长L的轻悬线固定于O点,在O点的正下方L/2处钉

题型:选择题

问题:

质量为m的小金属球可视为质点,用长L的轻悬线固定于O点,在O点的正下方L/2处钉有一颗钉子P,把悬线沿水平方向拉直,如图所示,竖直向下给小球一定的初速度v0,忽略空气阻力,则

A.小球从图示位置到最低点过程中,小球的速率可能保持不变

B.当悬线碰到钉子后的瞬时(设线没有断),小球的线速度突然增大

C.当悬线碰到钉子后的瞬时(设线没有断),小球的线速度突然减小到零

D.当悬线碰到钉子后的瞬时(设线没有断),小球的角速度突然增大

考点:角速度线速度周期、频率、转速
题型:选择题

阅读短文,将下面的课程表补充完整.

     The new school term is coming. Now the school clerks are planning a new timetable for Class 7, Grade 9.

     There are six classes every day, four in the morning and two in the afternoon. The students have a math

class every day. And they have seven English classes in a week. Two of them are given by a foreign teacher

and should be arranged (安排) together on Thursday morning.

     There are five Chinese classes in a week. Two of them should also be arranged one after the other for the

students to write their compositions.

     They have two physics classes in a week but on different days. Besides these, there is an art class every

Wednesday afternoon.

     It's necessary and important for students to take enough exercise. So they have two PE classes every week.

And they can do outdoor activities after school every afternoon.

      

题型:选择题

与乌头相反的药有()。

A.丹参

B.瓜萎仁

C.白及

D.浙贝母

E.玄参

题型:选择题

以下的说法错误的是()

A.恶性肿瘤患者机体的静息能量消耗高于或等于正常人群

B.高脂膳食可促进多种癌症的发生

C.恶性肿瘤患者多处于高代谢状态,蛋白质需要量增加

D.维生素E的重要作用是控制上皮组织分化,维持上皮组织细胞正常形态

E.膳食纤维通过影响肠蠕动和机体雌激素的生物利用率而降低患结肠癌和乳腺癌的风险

题型:选择题

在记账凭证编制的基本要求中规定,发现以前年度记账凭证有错误的,应当用蓝字填制一张更正的记账凭证。( )

题型:选择题

简述分馏塔启动前的操作步骤?

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