为了使单摆做简谐运动的周期变长，可以使（ ）
A．单摆的振幅适当加大
B．单摆的摆长适当加长
C．单摆从山下移到山上
D．单摆从北京移到南极
A、单摆的周期与振幅无关．故A错误．
B、将单摆的摆长加长，根据单摆的周期公式T=2π
知，周期变长．故B正确．L g
C、将单摆从山下移到山上，重力加速度减小，根据单摆的周期公式T=2π
知，周期变长．故C正确．L g
D、将单摆从北京移到南极，重力加速度变大，根据单摆的周期公式T=2π
知，周期变短．故D错误．L g
故选BC．
| Every group has a culture, however uncivilized it may seem to us. To the professional anthropologist, there is no intrinsic superiority of one culture over another, just as to the professional linguist, there is no intrinsic hierarchy among languages. People once thought of the languages of backward groups as undeveloped. While it is possible that language in general began as a series of grunts and groans, it is a fact established by the study of "backward" languages that no spoken tongue answers that description today. Most languages of uncivilized groups are, by our most severe standards, extremely complex. They differ from Western languages not in their sound patterns or grammatical structures, which usually are fully adequate for all language needs, but only in their vocabularies, which reflect the objects and activities known to their speakers. Even in this aspect, two things are to be noted. First, all languages seem to possess the machinery for vocabulary expansion, either by putting together words already in existence or by borrowing them from other languages and adapting them to their own system. Second, the objects and activities requiring names and distinctions in "backward" languages, while different from the West, are often surprisingly numerous and complicated. A Western language distinguishes merely between two degrees of remoteness ("this" and "that"). But some languages of the American Indians distinguish between what is close to the speaker, or to the person addressed, or removed from both, or out of sight, or in the past, or in the future. |
The author’s attitude shown in this passage toward "backward" languages is______.
A．restrained
B．subjective
C．objective
D．resolute
、
缺失，可摘局部义齿初戴一个月，咀嚼时常咬颊黏膜，下颌舌侧第一磨牙至磨牙后垫区压疼，来医院就诊。
过小