一辆载重货车驶过水门大桥时，交警示意停车．司机反应时间是0.5s，反应距离为12.5m．停车后查得该车的总质量为10t，车轮与地面的总接触面积为0.1m2．按照规定，该路段限速80km/h，对路面的压强不得超过7×105Pa．利用数据进行推算，说明货车被示意停车的可能有哪几种原因？（g=10N/kg）
v=
=s t
=25m/s=90km/h＞80km/h12.5m 0.5s
所以汽车超速．
P=
=F s
=106Pa＞7×105Pa10×103kg×10N/kg 0.1m2
所以汽车超载．
答：利用数据进行推算，货车被示意停车有2种原因：一是汽车超速．二是汽车超载．
| Before, whenever we had wealth, we started discussing poverty. Why not now Why is the current politics of wealth and poverty seemingly about wealth alone Eight years ago, when Bill Clinton first ran for president, the Dow Jones average was under 3,500, yearly federal budget deficits were projected at hundreds of billions of dollars forever and beyond, and no one talked about the "permanent boom" or the "new economy." Yet in that more straitened time, Clinton made much of the importance of "not leaving a single person behind." It is possible that similar "compassionate" rhetoric might yet play a role in the general election. But it is striking how much less talk there is about the poor than there was eight years ago, when the country was economically uncertain, or in previous eras, when the country felt flush. Even last summer, when Clinton spent several days on a remarkable, Bobby Kennedy-like pilgrimage through impoverished areas from Indian reservations in South Dakota to ghetto neighborhoods in East St. Louis, the administration decided to refer to the effort not as a poverty tour but as a "new market initiative." What is happening is partly a logical, policy-driven reaction. Poverty really is lower than it has been in decades, especially for minority groups. The most attractive solution to it — a growing economy — is being applied. The people who have been totally left out of this boom often have medical, mental or other problems for which no one has an immediate solution. "The economy has sucked in anyone who has any preparation, any ability to cope with modem life," says Franklin D. Raines, the former director of the Office of Management and Budget who is now head of Fannie Mae. When he and other people who specialize in the issue talk about solutions, they talk analytically and on a long-term basis: education, development of work skills, shifts in the labor market, adjustments in welfare reform. But I think there is another force that has made this a rich era with barely visible poor people. It is the unusual social and imaginative separation between prosperous America and those still left, out... It’s simple invisibility, because of increasing geographic, occupational, and social barriers that block one group from the other’s view. |
The author states that one important reason that we do not talk much about poverty is that ______.
A．no one knows what to do about it
B．poverty really is lower than in the past
C．no one has been left out of the current boom
D．the president is not concerned about the poor