问题 实验题

用“碰撞试验器”可以验证动量守恒定律,即研究两个小球在轨道水平部分碰撞前后的动量关系。

                                     

(1)试验中,直接测定小球碰撞前后的速度是不容易的。但是,可以通过仅测量      (填选项前的序号),间接地解决这个问题。

A.小球开始释放高度

B.小球抛出点距地面的高度

C.小球做平抛运动的射程

(2)图中O点是小球抛出点在地面上的垂直投影,实验时,先让入射球多次从斜轨上同一位置静止释放,找到其平均落地点的位置B,测量平抛射程。然后把被碰小球静止于轨道的水平部分,再将入射小球从斜轨上相同位置静止释放,与小球相撞,并多次重复。接下来要完成的必要步骤是     (填选项的符号)

A.用天平测量两个小球的质量

B.测量小球开始释放高度h

C.测量抛出点距地面的高度H

D.分别找到相碰后平均落地点的位置A、C

E.测量平抛射程

(3)若两球相碰前后的动量守恒,其表达式可表示为       (用(2)中测量的量表示);若碰撞是弹性碰撞,那么还应满足的表达式为       (用(2)中测量的量表示)。

(4)经测定,,小球落地点的平均位置到O点的距离如图所示。碰撞前、后­的动量分别为,则  :11;若碰撞结束时的动量为,则=11:   ;所以,碰撞前、后总动量的比值=   ;实验结果说明                     .

答案

(1)C                            ……………………(1分)

(2)D                            ……………………(1分)

(3)       ……………………(2分)

      ……………………(2分)

(4)14;2.9;;………(每空1分)

误差允许范围内,碰撞前、后的总动量不变.………(2分)

(1)设小球a没有和b球碰撞,抛出时速度为,球a和球b碰撞后抛出的速度分别为则我们要验证动量守恒即:,测速度是关键,平抛运动的初速度,因为平抛运动的高度一定,所以,即,只要测得小球做平抛运动的射程,即可替代速度。

(2)碰撞完毕后,就要测数据验证了,所以我们由(1)知道可以同过测量它们的射程就可以替代不容易测量的速度,

(3)见(1),弹性碰撞没有机械能损失,所以还应满足机械能守恒,

(4)将数据代入(3),因为存在试验误差,所以最后等式两边不会严格相等,所以误差允许范围内,碰撞前、后的总动量不变

完形填空

Gao Xiaosong was born with a silver spoon in his mouth. His grandfather was headmaster of the famous Tsinghua University. His wife’s father graduated from the Imperial College London and founded Shenzhen University. He basically grew up on Tsinghua's campus, and studied in the top schools in China, before he, unsurprisingly, entered Tsinghua's electronic engineering department, one of the school's best majors.

He wrote On the Same Page as You are at age 24. Almost overnight, every young person knew the song by heart. That tune and his later works made him a household name in the country. He later became a judge on the hot variety show (综艺节目) China's Got Talent. 

Everything has gone right for him aside from one major bump in the road—he was arrested for drunken driving in 2011, after he left the first press conference for his film, My Kingdom.

"For me, the six months was not only a result of the trial but also an atonement,(赎罪)" he says. "Six months is like a leaf falling from the tree of life—no big deal. I was a spoiled person in many ways before 40. So, maybe it was an opportunity to pay for my wildness and arrogance(傲慢) in my youth." The hardest thing for him in prison wasn't sleeping between a thief and a bad man but missing his daughter's development from ages 3.5–4.

Gao has become even busier after getting out of prison for drunken driving. A tour concert of his songs is going around the country, while Morning Talk airs weekly. He is searching for new vocal talent for a music company, and his next film is in progress. But he knows clearly what he wants from life—he plans to focus on music until he turns 60, after which he'll focus on writing and film directing. "You can never write pop music at 60," he says. "I don't complain about that. But you can always write a good book or direct a good film, no matter how old you are."

小题1:What caused him to become well-known to every family in China? 

(No more than 7 words)                                                  (3 marks)

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小题2:What did he find it the most difficult to do when he was in prison?

(No more than 11 words)                                                 (2 marks)

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小题3:When is he going to devote himself to writing and directing films ?

(No more than 7 words)                                                 (2 marks)

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小题4:What words can be used to describe Mr. Gao’s character before he was forty?

(No more than 6 words)                                                 (3 marks)

选择题