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问题 多选题

在滑冰场上，甲、乙两小孩分别坐在各自滑板上静止不动，在相互猛推一下对方后，两者分别向相反方向运动，且甲在冰上滑行的距离比乙远．假设两滑板与冰面间的动摩擦因数相同，则（　　）

A．甲推乙的时间等于乙推甲的时问

B．甲推乙的时间小于乙推甲的时间

C．在分开后，甲的加速度等于乙的加速度

D．在分开时，甲的初速度大于乙的初速度

答案

A、他们之间的力属于作用力和反作用力大小相等方向相反，作用时间也是一样长，所以他们受到的力是一样大的，时间也是相同的，故A正确，B错误

C、由于两与冰面间的摩擦因数相同，由牛顿第二定律可以知道，μmg=ma，所以a=μg，即他们的加速度的大小是相同的，故C正确；

D、由于甲在冰上滑行的距离比乙远，根据V2=2ax可知，在刚分开时，甲的初速度大于乙的初速度，故D正确

故选ACD．

单项选择题

微软前技术总监纳森·梅尔沃德2001年组建“智力风险”公司，雇用一群最聪明的人______生产技术专利，迄今已申请了价值8000万美元的专利，这证明“想法”并不______，到处都是，我们以为发明所必须具备的天才、专心、灵感和机缘巧合并不是______的。
依次填入划横线部分最恰当的一项是( )。

A．集体 虚幻 千载难逢
B．合作 遥远 遥不可及
C．批量 稀罕 必不可少
D．专门 离奇 不可替代
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单项选择题

A new study finds that blacks on death row (1) of killing whites are more likely to be executed than whites who kill minorities. It also concludes that blacks who kill (2) minorities are (3) likely to be executed than blacks who kill whites. For example, there is more than a twofold greater risk that an African-American who killed a white will be executed than a white person who kills a (4) victim. A Hispanic is at least 1.4 (5) more likely to be executed (6) such an offender kills a white.

The researchers of the study believe that there are two (7) explanations.. First, prosecutors often win (8) office if they win well-publicized cases. When a black kills a white, such killings gets more (9) and this idea can be (10) by many famous cases. (11) , the court judges at the state level are often (12) to elections, called retention elections. Retention election or judicial retention within the United States court system, is a periodic process, in which the voter (13) approval or disapproval for the judges presently (14) their position, and a judge can be removed from the position if the (15) of the citizens vote him or her out. Just as the researchers (16) out, death penalty is (17) political.

The findings of the study, in short, show that American justice systems clearly (18) white lives more than those of blacks or Hispanics. The researchers also say their findings (19) serious doubts about (20) that the U.S. criminal justice system is colorblind.

20（）

A.dissertations

B.affirms

C.claims

D.suggestions
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