首页
登录
职称英语
If a mother pushes her small son in a swing, giving only a light force each t
If a mother pushes her small son in a swing, giving only a light force each t
游客
2025-04-27
36
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. (328 words) [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
根据文章最后一段第一句和最后一句“An instrument called a tachometer makes use of the principle of resonance…These bars begin to move,and the resulting dial may be read to find the revolutions per minute of the motor very quickly.”可知,转速表利用了共振原理,它可以用 来测量发动机的转动速度。据此判断,答案是A。
转载请注明原文地址:http://tihaiku.com/zcyy/4055758.html
相关试题推荐
Yourkindnessingiving____totheconsiderationoftheaboveproblemwillbehi
Fewpeopledoubtthefundamentalimportanceofmothersinchild-rearing,but
Fewpeopledoubtthefundamentalimportanceofmothersinchild-rearing,but
Fewpeopledoubtthefundamentalimportanceofmothersinchild-rearing,but
Ifamotherpusheshersmallsoninaswing,givingonlyalightforceeacht
Ifamotherpusheshersmallsoninaswing,givingonlyalightforceeacht
Ifamotherpusheshersmallsoninaswing,givingonlyalightforceeacht
Ifamotherpusheshersmallsoninaswing,givingonlyalightforceeacht
ThetraditionalAmericanThanksgivingDaycelebration【1】to1621.【2】thatyear
ThetraditionalAmericanThanksgivingDaycelebration【1】to1621.【2】thatyear
随机试题
AlthoughMs.Brownfoundsomeofherdutiestobe______,hersupervisionoffor
Trialanderrorarethesourceofourknowledge.A、isB、wereC、hasD、havebeenA本
【L1】[br]【L10】[originaltext]Pressconferenceisanalltoofamiliarphenom
“因天材,就地利,故城郭不必中规矩,道路不必中准绳”的思想见于()。A.《周
以下可能会导致乳化沥青筛上剩余量试验结果偏小的情况是()。A.取样质量偏少
护士小王护理一位住在隔离病房的患者,她的做法不正确的A.从页面中间抓取避污纸
基础教育课程改革是一项系统工程,应始终贯彻( )的工作方针。A.先立后破,先实
李先生每月收入1万元,贷款20万元用于购买住房,采用等额本金还款法,期限10年,
A.维生素K B.鱼精蛋白 C.葡萄糖酸钙 D.氨基己酸 E.叶酸肝素过
企业战略管理的关键环节是()。A.战略制定 B.战略实施 C.战略控制
最新回复
(
0
)