测量动滑轮机械效率的实验中，需要测量的物理量是______、______、___

搜题请搜索小程序“爱下问搜题”

问题填空题

测量动滑轮机械效率的实验中，需要测量的物理量是______、______、______、______，然后根据公式______计算出机械效率．

答案

机械效率是指有用功与总功的比值，根据公式η=

W有

W总

可知，在实验中需要测量的物理量有物重G、拉力F、物体得升的高度h和绳端移动的距离s，然后利用公式才能得出机械效率的大小．

故答案为：物重G、拉力F、物体得升的高度h、绳端移动的距离s；η=

．

问答题简答题

延安精神的主要内容是什么？

查看答案

完形填空

完形填空。

Hi Cindy,
     Please don't worry if you feel a little strange around boys. You are in the process of   1   from a little girl
into a young womman and there are   2   called hormones (荷尔蒙) that are chaIlging not only your body but
your   3 . For example, you say you used to feel at ease   4   boys and you would usually run and fight one
another for   5 . That was Cindy, the little girl. The   6   woman doesn't want to fight boys or even run with
them   7   your interests are chaIlging. That is what is making you feel strange and it is also   8   to the other
girls around you and also to the boys. Your life is   9   a different stage but you should understand that this is
(a)  10  normal, and (b) something that will pass quickly.
     I think you should again try to  11  amund boys. You can still talk with them about  12  you like including
sports, movies, web sites and celebrities (名人). I  13  that you not try to fight with them, however, because
the  14  are becoming much bigger and stronger. I think you will find that you will  15  being with boys but
that your feelings will be different from the  16  they used to be I know you are not supposed to hve a  17
while you are still in school in China, but if you start to find some boys very handsome and you are strongly
18  to some of them, don't be surprised.  19 , this is all very normal. For now, you should  20  your school
work, though you will find that some boys are attracted to you. This will be a new adventure for you and my
best advice is to relax and enjoy it.
     Good luck!
                                                                                                                                                   Brad

( )1.A. starting
( )2.A. cells
( )3.A. mind
( )4.A. with
( )5.A. praise
( )6.A. brave
( )7.A. before
( )8.A. referring
( )9.A. entering
( )10.A. hardly
( )11.A. play
( )12.A. somebody
( )13.A. recommend
( )14.A. girls
( )15.A. hate
( )16.A. model
( )17.A. boyfriend
( )18.A. opposed
( )19.A. Rather
( )20.A. depend on

B. changing
B. nutritions
B. head
B. for
B. honor
B. unique
B. because
B. appealing
B. setting
B. possibly
B. relax
B. anybody
B. demand
B. adults
B. enjoy
B. standard
B. girlfriend
B. attracted
B. Besides
B. decide on

C. surviving
C. chemicals
C. life
C. against
C. good
C. smart
C. until
C. happening
C. reflecting
C. perfectly
C. date
C. something
C. command
C. boys
C. avoid
C. style
C. degree
C. exposed
C. Again
C. agree on

D. ranging
D. objects
D. study
D. without
D. fun
D. young
D. when
D. pointing
D. representing
D. nearly
D. fool
D. anything
D. determine
D. kids
D. regret
D. way
D. job
D. accustomed
D. Afterwards
D. concentrate on

查看答案