人在行走时,在伸出右手的同时,会伸出左脚,此时( )。
A.右手的角动量方向是竖直向上,左脚的角动量方向是竖直向下
B.右手的角动量方向是竖直向下,左脚的角动量方向是竖直向下
C.右手的角动量方向是竖直向上,左脚的角动量方向是竖直向上
D.右手的角动量方向是竖直向下,左脚的角动量方向是竖直向上
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人在行走时不会同手同脚的根本原因是( )。
A.转动定理
B.角动量守恒定律
C.调谐方程
D.动量守恒定律
用相同的力矩开门时,门的转动惯量越小,开门的速度越快,这句话反映了( )。
A.动量守恒定律
B.转动定理
C.冲量定理
D.角动量守恒定律
中国的冬季时,地球离太阳较近,阴历月较短。()
A. 对
B. 错
Listen to the passage twice and fill in the blanks with what you hear.Time is equal to everyone. Whether you are smart or foolish, ugly or beautiful, you have the same 24 hours each day that everyone else has. How you spend that valuable time determines the 1 . Time is more precious than any possession.There are three rules for effective time management. Firstly, don’t create 2 . Don’t try to work full time and take a full load. Be reasonable about how much work you can do.Secondly, make a list of all the things that you need to get done in a given time period. Put the tasks in order of _______3______and delete any unimportant items.Thirdly, avoid lack of focus. Use lists to 4 . To be more attentive, set boundaries with family and friends when you are at work, as personal phone calls and emails can easily disturb your workday progress. In a modern 5 , you can use technology to help. For unimportant communications, provide clients with a fax number or email address. This should cut down on the number of unimportant phone calls you receive throughout the day.