问题 选择题

为了安全,有些轿车装有倒车雷达,当轿车倒车时,尾部在非安全距离内遇到人或障碍物,雷达就会发出警报,方便司机判断车尾与后部障碍物间的距离.在倒车雷达工作过程中,应用了大量的物理知识,下列知识没有得到应用的是(  )

A.声音可以传递信息

B.声音可以传递能量

C.回声

D.超声波

答案

倒车雷达,即倒车防撞雷达,也叫泊车辅助装置,它能以声音或更为直观的显示告知司机车辆周围是否有障碍物,倒车时,利用超声波原理,由装置在车尾保险杠上的探头发送超声波撞击障碍物后反射此声波,计算出车体与障碍物间的实际距离,然后提示给司机,使停车或倒车更容易、更安全,所以说倒车雷达应用了回声定位的原理,获得一些信息.所以倒车雷达工作过程中,应用了超声波、回声、声音可以传递信息,没涉及到声音可以传递能量部分.

故选B.

单项选择题

Behind our house is the start of a fascinating trail (小径). This trail is one of the old roads that wind through untold miles of forest. My (36) , Beans, and I walk the trail frequently. Normally, Beans sniffs alongside the trail to follow the smell of a deer track or explore some cause known only to him.

Beans is a white dog, quite handsome and very smart. He not only understands what we tell him, but also often makes sounds as if he were trying to (37) back.

One morning, we took a different route, which led us to an unfamiliar trail. I was sure this trail would eventually lead us to our familiar (38) . But, no. We seemed to be far off course. After two hours, I suddenly realized that Beans probably (39) the way home. So I urged, "Beans, take me home." He ran down a new trail. But it merely led to an intersection (岔道口) of trails.

Soon it became (40) that we were getting nowhere. I began to picture the rest of the day in the (41) , without food or drink. We had walked about ten miles. But Beans seemed totally (42) The sniffing and exploring was going well for him.

Finally, we (43) a crossroad near a highway. Lady Luck suggested I should turn left. We did and (44) reached a cottage beside a field. I knocked on the door and explained my situation to an old man. He laughed and then drove us home.

Since our adventure, I (45) that Beans probably knew all along how to get home.

He was just having too much fan exploring new trails.

45()

A.regretted 

B.remembered 

C.concluded 

D.confirmed

问答题 简答题