如图所示，在离斜面底B点为L的O点竖直固定一长为L的直杆OA，A端_爱下问搜题

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问题填空题

如图所示，在离斜面底B点为L的O点竖直固定一长为L的直杆OA，A端与B点之间也用直杆连接．在杆上穿一光滑小环，先后两次从A点无初速度释放小环，第一次沿AO杆下滑，第二次沿AB杆下滑．重力加速度为g，则两次滑到斜面上所需的时间分别为t₁=______，t₂=______．

答案

沿AO杆下滑，加速度a=g，位移为L，则L=

1

2

gt12，解得t1=

2L

g

．

沿AB杆下滑，设∠OAB=α，则AB=2Lcosα，加速度a=

mgcosα

m

=gcosα．

根据2Lcosα=

1

2

gcosαt2，解得t2=2

L

g

．

故答案为：

2L

g

，2

L

g

．

阅读理解

完形填空。

     Nick is a 14-year-old school boy. His life is full of exams and studies on weekday. He has  1 free time.
He thinks playing computer games  2 the best way to make him relax. When he has free time, he sits in front
of the computer. Just  3   that way, he doesn't eat or drink for several hours.
     Last weekend, he played games on the computer again. He was too  4 and didn't want to move. He didn't
have  5 for six hours. When he had to go to the bathroom, he found he could not move. He  6 to the hospital.
The doctor told him he should have a good rest and  7 exercise.
    After coming back from the hospital. Nick follows the doctor's 8 . He often plays soccer with his friends.
9 sometimes he still plays computer games on weekends, he  10 does it for long. Now he lives a happy and
healthy life.

( )1. A. few
( )2. A. is
( )3. A. on
( )4. A. excite
( )5. A. something
( )6. A. is taken
( )7. A. pay attention to
( )8. A. dreams
( )9. A. Unless
( )10. A. ever

B. a few
B. are
B. for
B. excites
B. anything
B. was taken
B. paid attention to
B. advices
B. And
B. often

C. much
C. be
C. like
C. exciting
C. nothing
C. was taking
C. take care of
C. advice
C. Because
C. never

D. little
D. was
D. since
D. excited
D. everything
D. took
D. take out
D. hobbies
D. Although
D. always

判断题

患有性病的人更容易感染艾滋病。