题目

(1999年上海，25)一辆质量m=2 kg的平板车左端放有质量M=3 kg的小滑块，滑块与平板车之间的动摩擦因数μ=0.4.开始时平板车和滑块共同以v0=2 m/s的速度在光滑水平面上向右运动，并与竖直墙壁发生碰撞，设碰撞时间极短且碰撞后平板车速度大小保持不变，但方向与原来相反.平板车足够长，以至滑块不会滑到平板车右端.(取g=10 m/s2)求： (1)平板车第一次与墙壁碰撞后向左运动的最大距离.(2)平板车第二次与墙壁碰撞前瞬间的速度v.(3)为使滑块始终不会滑2、    Seniors Card is a partnership between the Queensland Government and participating businesses to provide discounts and Queensland Government concessions(price reductions)on a range of products and services to Queenslanders over 60．The project is FREE to join，and therefore you are not required to disclose your income．Your Seniors Card or Seniors Business Discount Card is convenient to use．Simply present your card at participating businesses to obtain discounts．     To receive a Seniors Card you must be a permanent resident of Queensland and be aged 60 or over     A Seniors Card is intended for all Queensland residents aged 60 and oven The Seniors Card gives access to government concessions as well as discounts at participating businesses in Queensland，some interstate discount and access to the FREE Senior Shopper service．     To receive a Seniors Card you must be a Queensland resident．Applicants for a Queensland Seniors Card must have their principal place of residence in Queensland for at least six months of the year．Additionally this address must be registered with at least one of the following government agencies： Electoral Commission of Queensland Centrelink Commonwealth Department of Veterans’ Affairs Queensland Transport  If you meet these criteria and your principal place of residence is in Queensland，you can apply for a card．However, if you live primarily in another Australian state，you will need to apply for a Seniors Card from the office closest to your home． 56．If you have a Seniors Card, you can           A．participate in businesses                           B．provide discounts   C．get free services everywhere                    D．obtmn some discounts or price reductions 57．To get a Seniors Card, you should            ．    A．have a registered address                         B．make your income known    C．be a Queenslander of at least sixty            D．five in Queensland for at least six months 58．The underlined word criteria in the last paragraph is closest in meaning to                A．requirements    B．wishes    C．1evels    D．needs