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
28
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
ExpenseAccountStatementEmployee:DaveLincolnDate:June27ReimbursableExp
Youwillhearfiveshortrecordings.Fivepeoplearegivingadviceonhowto
Whoistheauthor’sintendedaudience?[br]Inthispassage,whatadvicedoesth
水壶:开水()A.桌子:游戏 B.邮箱:邮件 C.磁带:磁盘 D.灌溉
一患者行烤瓷冠修复,冠就位后发现冠十分密合,经调无早接触后选择聚羧酸黏固剂黏固,
评估协会是评估机构和评估专业人员的自律性组织,依照( )实行自律管理。A、法律
当采用不平衡推力传递法进行滑坡稳定性计算时,下述说法中哪个不正确() A.当
男性,65岁,患糖尿病15年,高血压10年。查体:双下肢轻度水肿。尿蛋白(++)
治疗便秘常用的药引是A.生姜汤 B.绿豆汤 C.蜂蜜 D.白酒 E.淡盐
根据民法理论,民事法律行为的一般生效要件有( )。A.行为人必须具有完全民事行为
最新回复
(
0
)