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小明在做有关浮力的实验中,测得装满水的溢水杯重力为4.8N,空小桶重力为0.2N,把它们放在水平桌面上,如图甲所示.再将一个质量为400g的小球轻轻放入溢水杯中,小球沉到杯底,溢出的水全部流入小桶,如图乙所示.将装有溢出水的小桶挂在弹簧测力计下,静止时测力计的示数敷如图丙所示。ρ=1.0×103 kg/m3.求:

 

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    We all know the feeling: looking at the computer screen, pretending to be interested in our homework, even though we really feel bored. But such feelings may soon be at an end, says Dr. Harry Witchel, head of the Essex Medical School. He believes that computers of the future will notice when people feel bored and even take action to stopit.

    Before you get concerned, the machine won't be reading your mind. It will be observing the many movements you make while using a computer. It's not interested in the big movements needed to use the machine — like moving a mouse or touching a screen — but small, barely noticeable movements like closing your eyes, moving in your seat or rubbing your face. Witchel calls these “boredom movements" and says they show how interested the person is in what they are reading or watching. The higher the interest level, the less movement!

    To test his theory, Witchel invited 27 people to perform various computer-based tasks. The activities ranged from playing online games (an interesting task) to reading documents like government laws that most people would find boring.

A special video camera followed the participants' movements as they completed each task. Just as the researcher expected, the “boredom movements" greatly decreased, by as much as 42%,when the subjects were very interested in what they were reading or seeing.

    Fortunately, Dr Witchel isn't planning to use his results to create machines that report students who are not paying attention at school. Instead, he wants “movement sensing” technology to be built into future computers in order to improve students' computer-based learning experience.

    The scientist says that by measuring the students' interest level as they work, educators will be able to adjust their materials in real-time to keep students focused. Witchel also believes that the technology can provide filmmakers with honest audience opinions and in the future, help to develop more intelligent robots.