题干

(2011年陕西汉中模拟)在电梯中,把一重物置于台秤上,台秤与力传感器相连,电梯从静止加速上升,然后又匀速运动一段时间,最后停止运动,传感器的屏幕上显示出其受到的压力与时间的关系(N-t)图象如图3-3-9所示,则(  )

图3-3-9

A:电梯在启动阶段约经历了2.5秒的加速上升过程

B:电梯在启动阶段约经历了3.5秒的加速上升过程

C:电梯的最大加速度约为6.7 m/s2

D:电梯的最大加速度约为16.7 m/s2

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C

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    Have you ever run into a careless cell phone user on the street? Perhaps they were busy talking, texting or checking updates on WeChat without looking at what was going on around them. As the number of this new “species” of human has kept rising, they have been given a new name — phubbers(低头族).

    Recently, a cartoon created by students from China Central Academy of Fine Arts put this group of people under the spotlight. In the short film, phubbers with various social identities(身份) bury themselves in their phones. A doctor plays with his cell phone while letting his patient die, a pretty woman takes selfie in front of a car accident site, and a father loses his child without knowing about it while using his mobile phone. A chain of similar events eventually leads to the destruction of the world.

    Although the ending sounds overstated, the damage phubbing can bring is real.

    Your health is the first to bear the effect and result of it. “Constantly bending your head to check your cell phone could damage your neck,” Guangming Daily quoted doctors as saying. “the neck is like a rope that breaks after long-term stretching.” Also, staring at cell phones for long periods of time will damage your eyesight gradually, according to the report.

    But that's not all. Being a phubber could also damage your social skills and drive you away from your friends and family. At reunions with family or friends, many people tend to stick to their cell phones while others are chatting happily with each other and this creates a strange atmosphere, Qilu Evening News reported.

    It can also cost you your life. There have been lots of reports on phubbers who fell to their death, suffered accidents, and were robbed of their cell phones in broad daylight.