问题 选择题

如右图所示,一运送救灾物资的直升飞机沿水平方向匀速飞行.已知物资的总质量为m,吊运物资的悬索与竖直方向成θ角.设物资所受的空气阻力为F阻,悬索对物资的拉力为F,重力加速度为g,则(  )

A.       

B.

C.F=mgcos θ

D.

答案

答案:B

题目分析:以物资为研究对象,分析受力情况:重力mg、悬索对物资的拉力,空气阻力,根据平衡条件得知:mg与的合力与小相等,方向相反,则有

故选B.

点评:本题是实际的情景,实质是简单的物体平衡问题,分析受力、作出力图是关键.

单项选择题

案例五:一般资料:求助者,女性,37 岁,会计。案例介绍:求助者自述最近半年心烦,睡眠差,经常感到浑身不舒服,做事提不起精神。有时会心慌憋气。去医院检查,未发现明显器质性病变。但自己不相信,害怕自己有病,医生不说实话。丈夫也带她到多家医院,做了各种检查,同样也没有发现明显问题。医生针对她的症状开了一些药。服药后症状依旧,工作还经常出错。由其丈夫陪同前来咨询。心理咨询师观察了解到的情况:求助者性格内向,家境富裕,工作压力小,生活单调。下面是心理咨询师与求助者的一段咨询谈话:心理咨询师:您能详细谈谈您的睡眠情况吗?求助者:我一般十点左右睡觉,入睡没有问题。就是经常早上一两点钟就醒,醒了就再睡不着,睡不着就瞎想,真烦。心理咨询师:您烦,是因为失眠而烦吗?还是因为身体不舒服而烦?求助者:是因为浑身都不舒服。心理咨询师:您说您身体不舒服,可您去了很多家医院,该做的检查都做了,诊断没有病,这是怎么回事?求助者:我也不知道是怎么回事。心理咨询师:如果真有病,您吃了药是不是应该有所改变?可您还总是难受这是怎么回事啊?求助者:(沉默)……心理咨询师:您觉得会是所有的医生都诊断错了吗?求助者:应该不会,不会所有的医生都错,那我可能就是没病。心理咨询师:您想想如果一个和您年纪差不多的人。既要照顾住院的亲人,还得照顾孩子,还要工作,她会整天想着自己的不舒服吗?求助者:(点点头)是,忙起来就顾不了太多了,我可能确实太闲了。心理咨询师:这是不是应了一个说法,无事生非?求助者:(笑笑)有道理,那我得找点事做。心理咨询师:那倒用不着,您可以尽情地享受生活。如果真有病,该吃药还得吃药,但不要没病找病。您看我脂溢性脱发,这也是病,我能整天为脱发烦恼,到处寻医问药吗?求助者:听您这么说我就明白了,我以后只要有事,就全靠您了。

单选:该求助者社会功能的损伤程度可能是( )。

A.社会功能完好

B.轻度一中度受损

C.社会功能丧失

D.中度一重度受损

单项选择题

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