首页
登录
职称英语
If a mother pushes her small son in a swing, giving only a light force each
If a mother pushes her small son in a swing, giving only a light force each
游客
2025-04-25
32
管理
问题
If a mother pushes her small son in a swing, giving only a light force each time he returns, eventually he will be swinging quite high. The child can do this for himself by using his legs to increase the motion, but both the mother’s push and the child’s leg movements must occur at the proper moment, or the extent of the swing will not increase. In physics, increasing the swing is increasing the amplitude; the length of the rope on the swing determines its natural oscillation period. This ability of an object to move periodically or to vibrate when stimulated by a force operating in its natural period is called resonance.
Resonance is observed many times without consciously thinking about it; for example, one may find an annoying vibration or shimmy in an automobile, caused by a loose engine mount vibrating with increasing amplitude because of an out-of-round tire. The bulge on the tire slaps the pavement with each revolution; at the natural resonance point of the engine mount, it will begin to vibrate. Such vibrations can result in considerable damage if allowed to persist. Another destructive example of resonance is the shattering of a crystal goblet by the production of a musical tone at the natural resonant point of the goblet. The energy of the sound waves causes vibration in the glass; as its amplitude increases, the motion in the glass exceeds the elasticity of the goblet, and it shatters.
An instrument called a tachometer makes use of the principle of resonance. It consists of many tiny bars, loosely fastened together and arranged so that each bar can slide independently of the others. Movement of the bars causes changes in a dial. When placed next to a rotating motor or engine, the tachometer picks up slight vibrations which are transferred to the resonant bars. These bars begin to move, and the resulting dial may be read to find the revolutions per minute of the motor very quickly. [br] A tachometer is an instrument that uses resonance to determine ______.
选项
A、the speed of a motor in revolutions
B、the frequency at which a motor vibrates
C、the amplitude of an engine that oscillates
D、the changes in a dial within a car engine
答案
A
解析
转载请注明原文地址:https://tihaiku.com/zcyy/4052941.html
相关试题推荐
Doesanunbornbabyknowhismother’svoice?PsychologyprofessorAnthonyDeC
Doesanunbornbabyknowhismother’svoice?PsychologyprofessorAnthonyDeC
Doesanunbornbabyknowhismother’svoice?PsychologyprofessorAnthonyDeC
Doesanunbornbabyknowhismother’svoice?PsychologyprofessorAnthonyDeC
Doesanunbornbabyknowhismother’svoice?PsychologyprofessorAnthonyDe
Doesanunbornbabyknowhismother’svoice?PsychologyprofessorAnthonyDe
Doesanunbornbabyknowhismother’svoice?PsychologyprofessorAnthonyDe
Doesanunbornbabyknowhismother’svoice?PsychologyprofessorAnthonyDe
Doesanunbornbabyknowhismother’svoice?PsychologyprofessorAnthonyDe
IaskedmymotherifIcouldgoout,andshe______.A、descendedB、contentedC、co
随机试题
Readthearticlebelowaboutfoundationsofbusiness.Choosethecorrectwordor
下列属于行政处分的是()。A.拘留 B.罚款 C.降职 D.取消资格
在场地分析过程中,基于BIM技术结合()可对现场及拟建建筑物空间进行建模分析,结
男孩,2岁,于8月5日突然高热8小时,抽搐1小时,呕吐一次。查体:血压偏低,精神
《论语·述而》记载,孔子观赏一部乐舞后“三月不知肉味”,赞其“尽善尽美”。这部乐
糖酵解途径的关键酶是A.己糖激酶、6-磷酸果糖激酶-1、丙酮酸激酶B.己糖激酶、
根据继承法的有关规定,下列财产可以作为遗产继承的有( )。 A.自留地 B
知己知彼,才能百战不殆。这句话同样适用于人际交往之中,一个人只有先了解自己,才能
根据我国现行药品法律法规的规定,行政处罚的种类包括A.警告 B.罚款 C.拘
在Excel中,复制需要复制的内容后,在粘贴时,可以有选择的粘贴数值、格式或公式
最新回复
(
0
)