孙的笔画顺序是____。

如图1所示为某同学所安装的“验证牛顿第二定律”的实验装置．

①在“验证牛顿第二定律”的实验中，为了使小车受到合外力等于砝码和砝码盘的总重量，通常采用如下两个措施：

A．平衡摩擦力：将长木板无滑轮的一端下面垫一小木块，反复移动木块的位置，直到小车在砝码盘的拉动下带动纸带与小车一起做匀速直线运动；

B．在调整砝码多少的过程中，要保证砝码和砝码盘的总质量m远小于小车和砝码的总质量M．

以上哪一个措施中有何重大错误？（说明错误点）____

②如图2是上述实验打出的一条纸带，已知打点计时器的打点周期是0.02s，结合图乙给出的数据（单位cm），求出小车运动加速度的大小为____m/s²，并求出纸带中P点瞬时速度大小为____m/s（计算结果均保留2位有效数字）

       I just hope that our brains won’t crash(死机). Are you wo rking on your typing skills to make you a more efficient worker? That may be all for nothing as Intel believes that we’ll be able to control our computers with our brains by 2020.

       Intel and its resear ch partners are study ing how brain acts when it thinks. For example, scientists have found that people’s brains react in a similar manner when asked to think of a bear.

       Through sensors(感应器)that can find this sort of brain activity, Intel thinks that it will be able to read and translate this into an input system thanks to a c hip in the brain.

        “We’re trying to prove you can do interesting things with brain wav es. ”Intel research scientist Dean Pomerleau told Computerworld. “Eventually people may be willing to be, more devoted to brain implants(植入物). Imagine being able to surf the Web with the Power of your thoughts. ”

       Even if thin king about a bear isn’t enough to show that you want to copy and paste something. Intel still thinks that there’s a future in using your brain instead of the keyboard.

        “If we can get to the point where you can accurately find specific words, you could mentally type, ”he added. “You could compose characters or words by thinking about letters flashing on the screen or typing whole words rather than their individual characters. ”

       While this may all sound impractical for present time, Intel thinks that it’s possible and something we’ll all want.

        “I think human beings are unusually adaptive(适应的), ”said Andrew Chien, vice pre sident of research and director of future technologies research at Intel Labs. “If you told people 20 years ago that they would be carrying computers all the time, they would have said, ‘I don’t want that. I don’t need that. ’Now you can’t get them to stop carrying device s. There are a lot of things that have to be done first but I think implanting chips into human brains is well within the scope of possibility. ”

       Make good use of your favorite mouse and keyboard set-up before they’re old-fashioned.

同音字组词。

zhàng ____ 篷     赊 ____     膨 ____   ____ 碍     拐 ____

如图，则多边形的周长为 （   ）