一种氢气燃料的汽车,质量为m=2.0103kg,发动机的额定输出功率为80kW,

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问题:

一种氢气燃料的汽车,质量为m=2.0103kg,发动机的额定输出功率为80kW,行驶在平直公路上时所受阻力恒为车重的0.1倍.若汽车从静止开始先匀加速启动,加速度的大小为a=1.0m/s2.达到额定输出功率后,汽车保持功率不变又加速行驶了800m,直到获得最大速度后才匀速行驶.试求:

(1)汽车的最大行驶速度;

(2)汽车匀加速启动阶段结束时的速度;

(3)当速度为5m/s时,汽车牵引力的瞬时功率;

(4)当汽车的速度为32m/s时的加速度;

(5)汽车从静止到获得最大行驶速度所用的总时间.

考点:牛顿第二定律平均功率和瞬时功率的区别动能定理
题型:问答题

男性,30岁。吸烟8年,反复咳嗽、咳痰3年。2个月来发热,体温37.6~38.2℃,咳嗽加重,咳少量白痰,痰中偶带血丝,伴乏力、盗汗。关节酸痛,食欲稍减退,体重下降5kg。今晨漱口时突然咯鲜血,量约100ml。X线胸片发现左肺有片状阴影,其间有透亮区。

该患者大咯血最危险的并发症是()。

A.窒息

B.导致贫血

C.病灶迅速扩散

D.失血性休克

E.合并严重细菌感染

题型:问答题

临床资料:女,70岁,自诉确诊左足底恶性黑色素瘤两年余,中药治疗无明显好转来诊。超声综合描述:左腹股沟区可见多个低回声(图1),部分相互融合,最大3.5cm×2.1cm,边界清晰,形态不规则,内回声不均,CDFI:内可见血流信号。左腹股沟区另可见多个不均质回声区(图2),最大2.1cm×1.8cm,边界清晰,形态不规则,内可见无回声区,CDFI:不均质回声区内可见血流信号。超声提示()。

A.左腹股沟区多发不均质回声区(淋巴囊肿)

B.左腹股沟区多发不均质回声区(反应性淋巴结肿大)

C.左腹股沟区多发低回声、不均质回声(淋巴结转移瘤)

D.左腹股沟区多发不均质回声区(皮下血肿)

题型:问答题

请根据以下任务说明和写作要求,写一篇幅150词左右的英文短文。

Self – discipline (自律)

An elderly carpenter (木匠)was ready to retire. He told his employer his plans to leave the house building business and live a more leisurely (悠闲的) life with his wife. The employer was sorry to see his good worker go and asked if he could build just one more house as a personal favor. The carpenter said yes, but in time it was easy to see that his heart was not in his work. He built the house carelessly and used inferior (较差的) materials. It was an unfortunate way to end his career (职业). When the carpenter finished his work and the employer came to inspect (视察)the house and handed the front-door key to the carpenter. "This is your house," he said, "my gift to you."

What a shock! What a shame! If he had only known he was building his own house, he would have done it all so differently. Now he had to live in the home he had built none too well.

So it is with us. Think of yourself as the carpenter. Build wisely. It is the only life you will ever build. Your life tomorrow will be the result of your attitudes and the choices you make today.

1.以约30个词概括本文的故事;

2.以约120个词写一篇短文,包括如下要点:

(1)你读短文后的感想;

(2)叙述你的一次真实或虚构的对某一件事高度自律或负责的经历;

(3)那次高度自律或负责的经历对你的影响。

1.文中可使用自己的亲身经历或虚构的故事,可也以参照阅读材料的内容,但不得直接引用原文中的句子。

2.信中不能出现真实姓名和学校名称。

概括准确,语言规范,内容合适,篇章连贯。

题型:问答题

固定桥桥体应具备的条件,除了

A.桥体龈端必须与牙槽嵴黏膜接触
B.恢复缺失牙功能
C.符合口腔卫生条件
D.有足够的机械强度
E.使用材料应不损伤口腔组织

题型:问答题

栅比值的定义是()

A.铅条宽度与其间隔之比

B.铅条高度与其间隔物质高度之比

C.铅条高度与其宽度之比

D.铅条数与间隔数之比

E.铅条高度与其间隔距离之比

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