质量为8×107kg的列车,从某处开始进站并关闭发动机,只在恒定阻力作用下减速滑

题型:计算题

问题:

质量为8×107kg的列车,从某处开始进站并关闭发动机,只在恒定阻力作用下减速滑行。已知它开始滑行时的初速度为20m/s,当它滑行了300m时,速度减小到10m/s,接着又滑行了一段距离后刚好到达站台停下,那么:

(1)关闭动力时列车的初动能为多大?

(2)列车受到的恒定阻力为多大?

(3)列车进站滑行的总时间为多大?

考点:动能定理动能动量定理
题型:计算题

欠债不还,单方面撕毁合同等行为是[     ]

A.刑事违法行为

B.犯罪行为

C.民事违法行为

D.行政违法行为

题型:计算题

能使用CE级柴油机油的发动机,一定可以用CD级柴油机油替代。

题型:计算题

It is often observed that the aged spend much time thinking and talking about their past lives, (1) about the future. These reminiscences are not simply random or trivial memories, (2) is their purpose merely to make conversation. The old person’s recollections of the past help to (3) an identity that is becoming increasingly fragile: (4) any role that brings respect or any goal that might provide (5) to the future, the individual mentions their past as a reminder to listeners, that here was a life (6) living. (7) , the memories form part of a continuing life (8) , in which the old person (9) the events and experiences of the years gone by and (10) on the overall meaning of his or her own almost completed life.

As the life cycle (11) to its close, the aged must also learn to accept the reality of their own impending death. (12) this task is made difficult by the fact that death is almost a (13) subject in the United States. The mere discussion of death is often regarded as (14) As adults many of us find the topic frightening and are (15) to think about it—and certainly not to talk about it (16) the presence of someone who is dying. Death has achieved this taboo (17) only in the modern industrial societies. There seems to be an important reason for our reluctance to (18) the idea of death. It is the very fact that death remains (19) our control; it is almost the only one of the natural processes (20) is so.

Read the following text. Choose the best word (s) for each numbered blank and mark A, B, Cot D on ANSWER SHEET 1.18()

A.encounter

B.confront

C.tolerate

D.expose

题型:计算题

风疹与幼儿急疹的共同特点是()。

A.皮疹为红色斑丘疹,疹间皮肤正常

B.皮疹在1天内出齐

C.皮疹以躯干分布较多

D.疹退后无脱屑

E.伴有耳后、枕部淋巴结肿大

题型:计算题

两个简支梁的跨度、荷载、截面尺寸相同但所用材料不同,则两者相同的因素是()。

A.内力

B.反力

C.应力

D.位移

E.变形

更多题库