问题 计算题

在建的港珠澳大桥是连接香港、珠海、及澳门的大型跨海通道,全长50千米,主体工程由“海上桥梁,海底隧道及连接两者的人工岛”三部分组成.

(1)若一辆汽车以100千米/时 的平均速度通过港珠澳大桥,则需要   小时.

(2)为了了解大风对港珠澳大桥的影响情况,桥梁专家用鼓风机等设备对大桥模型进行抗风能力测试.通过调节鼓风机功率改变风力大小,观察桥梁模型晃动幅度,并绘制图象(如图甲).请结合图象说明大桥模型晃动幅度与风力大小有怎样的关系?                  

(3)当汽车进入海底隧道时,需要选择正确的照明方式以确保行车安全.汽车大灯通常有两种照明方式﹣﹣“远景照明”和“近景照明”,且“远景照明”时大灯的功率较大.如图乙是某汽车大灯的灯泡示意图,A和B是灯泡内的2条灯丝.通过开关S分别与触点“1”或“2”连接,使灯丝A或B工作,以改变照明方式.

已知灯泡的额定电压为12伏,灯丝A的电阻RA为1.2欧,灯丝B的电阻RB为1.6欧,电源电压U保持12伏不变,则当开关S与触点“2”接通时,汽车大灯处在哪种照明方式?通过计算加以说明.

答案

(1)0.5;(2)大桥模型晃动幅度随风力的增加先增大后减小,在10级风力左右晃动幅度最大;(3)当开关S与触点“2”接通时,汽车大灯处在“近景照明”

解:(1)此时通过大桥所用的时间是:t===0.5h;

(2)据图象能看出,此时大桥模型晃动幅度随风力的增加先增大后减小,在10级风力左右晃动幅度最大;

(3)当开关与触点1接触时,A灯工作,故此时的功率是:PA===120W;

当开关与触点2接触时,B灯工作,故此时的功率是:PB===90W;

因为S与触电2接触时的灯丝B工作,且PA<PB,故此时的照明方式是“近景照明”.

阅读理解

A young woman was driving through the lonely countryside. It was dark and raining. Suddenly she saw an old woman by the side of the road, holding her hand out as if she wanted a lift.

“I can’t leave her out in this weather,” the woman said to herself, so she stopped the car and opened the door.

“Do you want a lift?” she asked. The old woman nodded and climbed into the car. After a while, she said to the old woman, “Have you been waiting for a long time?” The old woman shook her head. “Strange,” thought the young woman. She tried again. “Bad weather for the time of year,” she said. The old woman nodded. No matter what the young woman said, the hitchhiker(搭车者) gave no answer except for a nod of the head or a shrug(耸肩).

Then the young woman noticed the hitchhiker’s hands, which were large and hairy. Suddenly she realized that the hitchhiker was actually a man! She stopped the car. “ I can’t see out of the rear screen,” she said, “Would you mind clearing it for me?”

The hitchhiker nodded and opened the door. As soon as the hitchhiker was out of the car, the terrified young woman raced off.

When she got to the next village she pulled up. She noticed that the hitchhiker had left his handbag behind. She picked it up and opened it. She gave a gasp. Inside the bag was a gun.

小题1:The woman stopped the car because _______.

A.the old woman asked her to

B.she recognized the old woman

C.she knew what the woman wanted

D.she wanted to helped the old woman小题2:What made the woman feel strange about the old woman?

A.That she kept nodding her head

B.That she was unable to speak

C.That she gave no answer to her questions

D.That she had large and hairy hands小题3:The young woman asked the hitchhiker to clear the rear screen because _______.

A.this is the way she thought of to get rid of him

B.the hitchhiker frightened her

C.the hitchhiker was very helpful

D.she couldn’t see out of the rear screen小题4:The hitchhiker left the bag with a gun in it behind because_______.

A.he wanted to give her a warning

B.he had not expected the woman would leave him behind in the rain

C.it was his present for her

D.he wanted to kill her with the gun

单项选择题