问题
选择题
如图所示，小船被绳索牵引着匀速靠岸，若水的阻力不变，则
A．绳子张力不变
B．绳子张力不断减小
C．船所受浮力不变
D．船所受浮力不断减小
答案
答案：D
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如图所示，小船被绳索牵引着匀速靠岸，若水的阻力不变，则
A．绳子张力不变
B．绳子张力不断减小
C．船所受浮力不变
D．船所受浮力不断减小
答案：D
| Questions 11-15 are based on the following passage. Davis, California, like many other American cities, has been threatened by unchecked growth, swarming automobiles, and steeply rising energy costs. But unlike towns and cities which leave energy policy to the federal government or energy corporations, the citizens of Davis have acted on their own. After lengthy debate, Davis’ City Council moved to curb growth. It turned against the automobile and embraced the bicycle as a means of transport. It sponsored an inquiry into energy uses and endorsed a series of measures aimed at reducing energy consumption by as much as one half. It cut back the use of petroleum-derived pesticides on the thousands of trees and shrubs that shade the city’s streets, adopting instead a policy of biological control for insects. The city’s own cars and trucks have been transformed into a fleet of compact vehicles. When a Davis employee has to get around town, he borrows a bike from the city rack. Davis even passed a law formally and solemnly sanctioning the clothesline. The citizens of Davis have been involved in progressive city planning and energy conservation since 1968, when they persuaded the City Council to facilitate bicycle transportation by developing a system of bikeways. The City’s general plan for development, drawn up in 1972, was based on questionnaires distributed to residents. When a survey of residents showed that automobiles represented 50 percent of energy consumption and space heating and cooling accounted for 25 percent, transportation and building construction became important focal points in the Davis plan. Armed with survey information revealing that a building’s east-west orientation on the lot, as well as its insulation, window area, roof and wall colors, overhang shading, and other factors greatly influenced space heating and cooling needs, the City Council drew up a building construction code which greatly reduced the cost of winter heating and eliminates the need for air conditioning even on Davis’ hottest (114°) day. To demonstrate to local builders and developers methods for complying with the new code, Davis built two model solar homes, a single-family dwelling which takes advantage of natural southern exposure sunlight and a duplex adaptable to difficult siting situationswhere direct sunlight is blocked．Many of Davis’measures simply facilitate natural solar heating or sun-shading. Where most communities require that fences be built close to houses, Davis realized that practice meant blocking winter sunlight. New fences in Davis must be placed closer to the street, giving residents the benefit of natural solar heat in winter. Reducing required street widths provides more shade and saves asphalt to boot. Davis’ other energy conserving moves run the gamut—from a city ordinance encouraging cottage industry (to cut down on commuting and the need for new office building construction) to planting evergreens on city streets to reduce leaf pickup in the fall, from a ban on non-solar swimming pool heaters to a recycling center that supports itself by selling $3,000 worth of recyclables a month. |
It appears that Davis is______.
A．a "good old American town"
B．committed to social justice
C．a medium-to-small-size city
D．blessed by a p radical element in the population