问题 探究题

目前汽车刹车器均采用油压制动.油压制动刹车时消耗的机械能以内能形式排放掉,形成能源的浪费.现有一种汽车再生制动器,能把汽车刹车制动时消耗的机械能转化为电能而储存起来,有效地利用了能量.实际上汽车刹车时再生制动器无法提供足够的刹车阻力,仍需要与油压制动器配合使用,产生恒定的刹车阻力来满足刹车要求,若某汽车以72km/h的速度行驶,刹车时再生制动器产生的阻力随时间变化的关系如下表:

①汽车刹车时,再生制动器所产生的刹车阻力大小随时间的变化情况是_____

A.逐渐增大

B.先增大后不变

C.先增大后减小

D.先增大后不变再减小

②在图甲中作出汽车刹车时再生制动器0~0.8s内产生的刹车阻力随时间变化的图象.

③如果汽车制动时需要产生恒定的刹车阻力为1×104N,由图甲可知t=0.5s时再生制动器产生的刹车阻力_____N,此时油压制动器还需产生_____N的刹车阻力.

④在满足③的刹车阻力作用下,汽车的行驶路程与时间变化的关系如图乙所示,则在0~0.5s内汽车克服刹车阻力所做的功W=_____

答案

①D;

③8.6×103;1.4×103(从图上读数可以略有不同,所以答案不唯一);

④1×105J

完形填空

In the summer vacation of 1997 , I was fixed with a job . I worked as a(n)     36   at Mr. Breen’s fruit shop .The fruit shop did    37    business . Most of the trade came from the housewives who lived in the neighbourhood,     38    he also had regular customers who arrived outside the shop in cars . Mr Breen    39    them all by name and they sometimes even had their order already made up , always     40   me to carry it out to their car . They were clearly long-standing customers , and I    41    they must have stayed faithful to him   42     he had promised to sell good quality     43   . He had a way with them —I had to   44     that . He called every woman “madam” for a start ,    45    those who clearly were not, but when he     46   it , it did not sound like flattery (奉承). It just sounded     47   in an old-fashioned way . He was a great chatter     48   . If he did not know them , he would greet them with a few    49    about the weather ,     50   he did , he would ask about their families or make    51    , always cutting his cloth    52    his customers . Whatever their bills came to , be     53   gave them back the few odd pence (零钱), and I am sure they thought he was very generous (慷慨). But I thought he was the opposite . He never    54    anything away . He was always looking for     55   for nothing .

36.A.operator        B.assistant      C.waiter              D.secretary

37.A.good           B.poor        C.big                 D.usual

38.A.so                 B.when          C.therefore          D.but

39.A.sold           B.knew          C.gave          D.sent

40.A.making        B.letting       C.getting             D.keeping

41.A.wish          B.insist         C.declare        D.suppose

42.A.when         B.if              C.because            D.though

43.A.food          B.fruit            C.vegetables   D.drink

44.A.admit         B.expect         C.announce   D.promise

45.A.yet            B.only            C.just                D.even

46.A.told           B.said                C.spoke        D.talked

47.A.serious          B.strange        C.polite             D.familiar

48.A.as well          B.as usual     C.either             D.also

49.A.sayings          B.questions   C.words        D.speeches

50.A.and then        B.and so       C.even if            D.but if

51.A.preparations   B.jokes           C.repairs       D.friends

52.A.according to   B.due to                C.instead of  D.up to

53.A.never           B.ever            C.seldom             D.always

54.A.took          B.moved       C.threw       D.turned .

55.A.something      B.anything      C.somebody  D.anybody

单项选择题