航模兴趣小组设计出一架遥控飞行器，其质量m=2kg，动力系统提供的恒定升力F=28N．试飞时，飞行器从地面由静止开始竖直上升．设飞行器飞行时所受的阻力大小不变，g取10m/s²． $\mathrm{}{}^{\mathrm{}}$

2014年对中美关系而言是极不平凡的一年。一方面经贸合作是中美关系的“压舱石”，另一方面中美之间的战略互疑却仍然很深，中美在亚太地区的战略博弈有不断深化的趋势。对中美关系的研判正确的是（    ）
①中美关系仍处于竞争与合作的互动平衡当中                      ②中美双方应该进一步增进互信，相向而行
③中美关系健康发展有利于世界的和平与发展                      ④中国取代美国霸主地位才能维护新兴国家利益

    For years, I followed the materialistic standards around me. I thought that without the purses, shoes, and all the other “1” things, I would not be as pretty, smart, or important as others of my age.

    As a freshman (新生) of my high school, I thought top social status could be gained by doing everything to 2. So I became a(n)3 and bought fake (伪造的) designer purses. I felt popular and important, and I4 it.

    But, my parents couldn't understand my strong 5to be someone just to 6 others. They tried endlessly to convince me that I was hurting myself,7 I wouldn't listen. I felt 8 with this way of my life until one day I looked at myself in the mirror and saw someone with makeup and the product-filled hair wasn't me. That person was 9.

    So I quit cheerleading and 10 swimming again, something I had loved for eight years before high school. I also attended my school's top vocal (声乐) performance group, and 11 myself whole-heartedly to community service.

    I wrote articles in my school newspaper that questioned the materialistic 12 of many students at my school. I started 13 my limits academically, which I14 considered less important than improving my social status.

    I found a new group of friends who15 me, unlike my old friends. I found I no longer needed to impress others materialistically. Starting over was 16. My classmates looked at me as if they didn't know me.

    I am to 17 the materialistic culture. I am confident, talented, and optimistic. I know who I am. I'm motivated to explore even more of my 18 as a student and a member of my community.

    I took one of the worst 19 in my life but I turned it around and 20 something beautiful——a life that fits me, with meaning and happiness.