题目

天花板下悬挂着两个固定的光滑裸露导线圆环半径为r=0.5m,相距L=1m,然后连接电路,电源电动势E=3V,并且放入一个竖直向上的匀强磁场,B=0.4T.现在将一根质量m=60g,    电阻R=1.5Ω的金属棒搁置其上.闭合开关后,金属棒会上滑一定距离最后静止在圆环某位置.问此金属棒上升高度H=?此过程安培力做功W=?(不计其它电阻,重力加速度g=10m/s2)Recently I fully understood that a little favor could really make a big difference. My daughter and I were, accidentally, in time to catch a falling heart just before it hit the ground.It all started when Charlene, one of my co-volunteers at the library, asked if I could do her duty on Tuesday since her doctor appointment had been unexpectedly changed. I agreed, which meant I  was home on Friday instead of volunteering as previously planned.My daughter, Mary, managers a book store in town. Mid-morning, she called to ask me for help. Would I buy a fifty dollar gift card, birthday card, and cake for one of Mary’s assistant managers, Cindy?Mary explained she had to call Cindy in to take the place of another assistant manager who was sick, but felt terrible about it when she discovered it was Cindy’s birthday. Cindy insisted that it was just fine. But that was not what Mary thought, so she gathered enough money from other employees to throw a surprise party for Cindy. Since neither Mary, nor any of the other employees, could leave to pick up the goodies, they were turning to me for help. Days later, Mary told me the wonderful rest of the story, “Cindy cried and cried when we surprised her. After the party, Cindy told us that her boyfriend had chosen that morning to break up with her. To top that off, she only had 26 cents left in her bank account.”We were surprised at the series of unexpected events that took place in order to circle Cindy with love and catch her falling heart just before it hit the ground.【小题1】Why did Charlene ask a favor of the writer?A．ShehadtoseethedoctoronFriday. B．Shewantedtocelebrateherdaughter’sbirthday.C．ShehadanunexpectedappointmentonTuesday.D．Sheneededtoprepareforherdaughter’sbirthday.【小题2】What can we learn about Mary?A．Shewasalearned careerwoman.B．Shehaduneasyrelationshipswithherassistants. C．SheknewCindy’slovestorybeforethesurpriseparty.D．Sheplayedthemostimportantroleinthiscircleoflove.【小题3】Which of the following couldn’t be the reason why Cindy cried?A．She had to work on her birthday.B．She had little money in her bank account.C．She was greatly moved by Mary’s care and kindness.D．She and her boyfriend parted that very morning.【小题4】The underlined word “goodies” refers to_________.A．Gifts for CindyB．Good storiesC．Close friendsD．Goods on sale