题目

如图所示，轻杆在其中点O折成900后保持形状不变。O点安有光滑的固定转动轴，两端分别固定质量为m1.m??2的小球A.B（m1 ＞ m2），OA处于水平位置。无初速释放后，该装置第一次顺时针摆动900过程中，下列说法正确的是： A．小球1的总机械能守恒 B．A球机械能的减少大于B球机械能的增加 C．A球机械能的减少小于B球机械能的增加 D．A球机械能的减少等于B球机械能的增加阅读下列短文，从每小题所给的A、B、C、D四个选项中选出一个最佳选项。Let’s Explore(探究)The Nature!Are you interested in animals and nature? Want to enjoy your summer holiday and learn something interesting and useful?Here comes your CHANCE! Youth Explorer has prepared you with a THREE—DAY SUMMER PROGRAM! You can take part in many hands-on activities and meet with live animals-giraffes，pandas，tigers，zebras and so on．More information about the program is as follows：Age：Students aged 8一16．Groups：There are 2 programs for yon to choose from．Each program needs at most 15 students．Program AProgram BDates：14一16 July，2014Dates：5—7 August．2014Days：Monday to WednesdayDays：Tuesday to ThursdayTime：10：00 a．m．一4：00 p．m．Time：1O：00 a．m．一4：00 p．m．Program cost：$230 for members：$250 for non-members．How to do：simply come to our centre to get an application form (申请表)．send your completed form on or before 1lth July，2014(Friday)．Notes：1．NO FREE LUNCHES ARE PROVIDED because of personal food differences．Yon may either bring a lunch-box or pay for lunch at our restaurants．2．Both programs will start l DAY later if there is a warning of rainstorms．COME AND JOIN US NOW! DONT MISS THE CHANCE !1.Who can join the three-day summer programs?A．A kid of 7 B．A girl of 17C．A boy of 14 D．A man of 262.Free lunches aren't provided because_________．A．the lunches cost too much B．people have different tastesC．there are many restaurants D．They may bring lunch—boxes3.What can we know from the passage?A．Youth Explorer is the name of the program．B．More than 15 students are in each program．C．We can see three kinds of animals in the program．D．You need to hand in an application for the program．