题干

1966年,在地球的上空完成了用动力学方法测质量的实验.实验时,用双子星号宇宙飞船m1去接触正在轨道上运行的火箭组m2(后者的发动机已熄火).接触以后,开动双子星号飞船的推进器,使飞船和火箭组共同加速.推进器的平均推力F=895N,推进器开动时间△t=7s.测出飞船和火箭组的速度变化△v=0.91m/s.已知双子星号飞船的质量m1=3400kg.由以上实验数据可测出火箭组的质量m2为(   )

A:3400kg

B:3485kg

C:6265kg

D:6885kg

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B

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    Every kid wishes to be an adult. Do you remember playing house as a child — pretending(假装) to be a grown-up like your parents? Did you imagine you were a doctor, a soldier or a teacher? At that time, anything seemed more exciting than being young.

    But now as grown-ups, some adults find they cannot leave childhood behind. They become “kidults”. Being a kidult has become a lifestyle choice among young people across Asia.

    Some kidults collect toys they once played with. Hello Kitty, Garfield, and Snoopy have many adult fans around the world. It is not unusual to see a 20-something woman with a big, Garfield-shaped cushion on her sofa or a Hello Kitty mobile phone accessory(配件、附件).

    Other kidults still enjoy children's stories and fairy tales. For example, the British publisher Bloomsbury even released an edition(发布一个版本) of the Harry Potter novels with an adult cover. That way, no one else on the subway will know that an adult is actually reading a children's book.

    “Kidults can be like vitamins to society. Adults who love their childhood most and hold on to pure, child-like emotion may be needed in such a rough and dry society,” said Lee So-jung, a professor at Hankuk University of Foreign Studies.

    He added that kidult culture may fill the generation gap between adults and kids. It could give children and their parents books, movies, and cartoon shows to enjoy together.

    Tim Greenhalgh, an adviser in London explained that some kidults just refuse to grow up. They hold on to childhood because working life in a busy and stressful city frightens them. Kidults would like to forget their age and openly show their fear of society and adulthood.

    “So, they can escape from increasingly busy and stressful lives that are hard to deal with,” Greenhalgh said.