题目

自行车以5m/s的速度匀速追赶停在前方的汽车，当追赶到离汽车还有20m时，汽车以1m/s2的加速度匀加速启动．求： （1）当汽车的速度达到5m/s时所需的时间； （2）在这段时间内自行车的位移； （3）在这段时间内汽车的位移； （4）自行车能否追上汽车． 答案：匀变速直线运动的位移与时间的关系；匀变速直线运动的速度与时间的关系． 【分析】（1）由匀变速直线运动的速度公式可以求出汽车运动的时间． （2）由匀变速直线运动的位移公式可以求出汽车的位移． （3）由匀速直线运动的位移公式可以求出自行车的位移． （4）根据汽车与自行车的位移关系CIn March, New York City Mayor Bill de Blasio ended a decade-long citywide ban on cellphones in public schools and left them to make up their own rules because he argued that by denying access for some students, the city was exacerbating(使加重) the achievement gap in students’ performance.Two researchers from the London School of Economics, Richard Murphy and Louis-Philippe Beland argued that this might have the opposite effect because students are not generally using their phones to assist in their classroom work during school. "Schools could significantly reduce the education achievement gap by prohibiting cellphone use in schools, and so by allowing phones in schools, New York may unintentionally increase the inequalities of outcomes," they told CNN.However, some educators have come to embrace the technology in their students’ pockets. Teacher Ken Halla has been teaching world history and Advanced Placement for 22 years but his students’ cellphone ownership forced him to adapt to his classroom dynamics where he no longer is the single authority lecturing, according to the National Education Association (NEA). He now roams(漫步) the classroom and encourages students to use their cellphones to help them complete their assignments, this way they are less likely to let their devices distract themselves."It’s harder to do negative behavior when the phones are out and the teacher is walking around," Mr. Halla told the NEA. "I’ve always been that type of person who likes to adapt and change as time goes on. Otherwise, I wouldn’t still be teaching many years down the road."【1】Why was the ban on cellphones stopped in New York public schools?A. It negatively affected students’ health.B. It limited most students’ progress.C. It brought about unexpected side effects.D. It was requested by parents and students.【2】How did the two researchers find New York’s act?A. Appreciative. B. Meaningless. C. Impractical. D. Worrying.【3】What is Halla’s class like?A. Students can solve problems using cellphones.B. Students can use cellphones at will.C. The class focuses on how to use cellphones.D. He is the only center of the entire class.【4】What does the phrase "that type of person" in the last paragraph refer to?A.A tolerant one. B.A humorous one.C. An easy-going one. D. An open-minded one.