搜题请搜索小程序“爱下问搜题”
问题 选择题

一物体从静止开始，所受的合力F随时间t变化图线如图所示，规定向右为正方向．则该物体在4秒内的运动情况是（　　）

A．物体在1～3s内做匀变速直线运动

B．物体在0～2s内向右运动，2～4s内向左运动

C．物体在0～l s内加速运动，1～2s内减速运动

D．物体在0～4s内一直向右运动

答案

A、物体在1～3s内受到的合外力是个变力，先减小后反向增大，所以加速度先减小后反向增大，不是匀变速，故A错误；

B、在0～2s内，物体受到向正方向的合外力作用，物体向正方向做加速直线运动，在2～4s内，物体受到向负方向的合外力作用，物体继续向正方向做减速直线运动．故BC错误，D正确；

故选D

单项选择题

One of the most authoritative voices speaking to us today is, of course, the voice of the advertisers. Its shrilling clamor dominates our lives. It shouts at us from the television screens and the radio loudspeakers; waves to us from every page of the newspaper; plucks at our sleeves on the escalator; signals to us from the road-side billboards all day and flashes messages to us in colored lights at night. It has forced on us a whole new conception of the successful man as a man no less than 20% of whose mail consists of announcements of giant carpet sales.
Advertising has been among England’s biggest growing industries since the war, in terms of the ratio of money earnings to demonstrate achievement. Why all this fantastic expenditure
Perhaps the answer is that advertising saves the manufacturers from having to think about the customer. At the stage of designing and developing a product, there is quite enough to think about without worrying over whether anybody will want to buy it. The designer is busy enough without adding customer-appeal to all his other problems of man-hours and machine tolerances and stress factors. So they just go ahead and make the thing and leave it to the advertiser to find eleven ways of making it appeal to purchasers after they finished it, by pretending that it gives status, or attracts love, or signifies manliness. If the advertising agency can do this authoritatively enough, the manufacturer is in clover (养尊处优).
Other manufacturers find advertising saves them from changing their product. And manufacturers hate changes. The ideal product is one or another, some alteration seems called for--how much better to change the image, the packet or the pitch (促销宣传) made by the product, rather than go to all the inconvenience of changing the product itself.

According to the passage modern advertising is "authoritative" because of the way it

A．influences our image of the kind of person we ought to be like.

B．interferes with the privacy of home life.

C．continually forces us into buying things.

D．distracts us no matter where we travel.
查看答案
名词解释

金关工程
查看答案