题干

某同学利用打点计时器和气垫导轨做“探究碰撞中的不变量”的实验,气垫导轨装置如图1甲表示,所用的气垫导轨装置由导轨、滑块、弹射架等组成.在空腔导轨的两个工作面上均匀分布着一定数量的小孔,向导轨空腔内不断通入压缩空气,压缩空气会从小孔中喷出,使滑块稳定地漂浮在导轨上,如图1乙所示,这样就大大减小因滑块和导轨之间的摩擦而引起的误差.

上一题 下一题 0.0难度 选择题 更新时间:2016-01-22 03:39:16

答案(点此获取答案解析)

同类题1

    To most of us, school means classes, teachers, schedules, grades, and tests. But for the children at Sudbury Valley School in Massachusetts, school is very different.
    Firstly, there are no lessons. All the children, aged between 4 and 19, do whatever they want. There are no teachers, only “staff members (职员)”. The idea behind this is that you do not need to make children learn, because children want to learn anyway. “You do not need to say to a three-year-old. ‘Go explore your environment."You can't stop them!” says Daniel Greenberg, a founder of the school. “But if you make children do what you want all day, they will lose all taste for learning.”
    At Sudbury Valley School, you will allow children to talk, read, paint, cook, work on computers, study French, play the piano, climb trees, or just run around. Two boys spent three years just fishing!
    The other way that Sudbury Valley School is different is that the children can decide the rules. Every week, there is a school meeting where both children and staff have one vote each — even the four-year-olds. They decide the school rules, how to spend the school budget(预算), and even which staff they want and do not want any more.
    When the school first opened in 1968, people said it would never work. But today, the school has 200 students, and 80% of its students go on to college. Even the two boys who went fishing all time have successful careers today. One of them is a musician and the other is a computer scientist.