大学物理简明教程课后习题及答案 - 百度文库 ر

???2˵A1A2нΪ

??񶯵λΪ. 228-7 򵥵ķг񶯺ϳɺú񶯵

????x?5cos(3t?)cmx?5cos(3t?)cm?1?133(1) ? (2)? 7?4??x2?5cos(3t??x2?5cos(3t?)cm)cm33??7??⣺ (1) ????2??1???2?,

33 A?A1?A2?10cm

4??(2) ??????,

33 A?0

8-8 һʵͬʱͬһֱϵļг񶯣񶯷Ϊ

??x?0.4cos(2t?)m?16 ?5?x2?0.3cos(2t??)m6?Էֱתʸ񶯺ϳɷ񶯵񶯷ͳ࣬дг񷽳̡

5?(??)?? 66 A?A1?A2?0.1m

⣺ ????5?Asin?1?A2sin?266?3 tan??1??5?A2cos?1?A2cos?230.4cos?0.3cos66? ??

60.4?sin?0.3sin񶯷Ϊ

?x?0.1cos(2t?)m

6(ͼ)

9-1 񶯺Ͳʲôϵ?ƽг̺ͼг񶯷ʲôͬ?ʲôϵ?ߺͲʲôͬ?

: (1)ָһϵͳ(ҲǽеһԪ)ij̶ƽλø˶ϵͳ뿪ƽλõλʱԺɱʾΪy?f(t)еĴ̣ʱԪڸԵƽλø񶯣˽һԪ뿪ƽλõλƼλxʱtĺy?f(x,t) (2)г񶯷y?f(t)ֻһıʱtǽһԪƫƽλõλʱ仯Ĺɣƽгy?f(x,t)λxʱtǽԪƫƽλõλʱ仯Ĺɣ

ѡ

xy?Acos?(t?)uеλø󣬼ɵõõ񶯷̣Դֵг

ϵDzıҪ֮һ

(3)y?f(t)һʵλʱ仯ĹɣˣΪyΪty?f(x,t)ǽԪλλãʱ仯Ĺɣ

ΪyΪxÿһͼֻܸijһʱԪλλx仯Ĺɣֻܸijһʱ̵IJͼͬʱ̵IJ߾Dzͬʱ̵IJͼ

xxu)+?0еuʾʲô?дΪy=Acos 9-2 y=Acos?(

?x?xxt??t???0u)+?0ݵֵu()uʲô˼?txӣӦģ?(

t?䣬ɴܴӲ˵ʲô?

?x: еx/uʾ˽λΪxԪԭʱ䣻u

ʾxԪԭλࣻtʱ̵IJΪ t??tʱ̵IJΪ

yt?Acos(?t??xu??0)

yt??t?Acos[?(t??t)??(x??x)u??0]

)x?tx?u?ttuʾʱ̣λô״̬󴫲У?x(?t?)uֵ仯˵˾ʱ?tμǰtxʱ

?xy?Acos(?t???0)?x?u?tu˵ľ룬˵һнеIJν֮

̣

9-3 פڲڼͬһ벨ϣʵ񶯵ʲôͬʲôͬ?

(?t??x?: ȡפΪ֪еͬһ벨ϣ

ʵDzͬģʵλðҹɱ仯ģ仯?ͬһ벨ϣʵλͬģɱʾΪ

ڵĽΪһΣͬһνڸʵ㶼ͬλ࣬νڵʵλ෴

9-4 ֪ԴԭһƽгΪy=Acos(Bt?Cx)AB

y?2Acos2?xcos??vt2Acos2?xCΪֵ

(1)١Ƶʡ벨

(2)дϾ벨ԴΪlһ񶯷̣ (3)һʱ̣ڲĴΪdλ : (1)֪ƽгIJ

y?Acos(Bt?Cx) (x?0)

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ʽ벨̵ı׼ʽ

y?Acos(2??t?2?Ƚϣ֪ ΪAƵ

x?

B2?

)??2?Bu????CC

12?T???B

(2)x?l벨̼ɵõõ񶯷 y?Acos(Bt?Cl)

(3)һʱtͬһ֮λΪ

2????(x2?x1)?? x2?x1?d

???2?Cʽ

???Cd

9-5 ӴƽгIJΪy=0.05cos(10?t?4?x)ʽx,y׼ƣtƣ

(1)IJ١ƵʺͲ

(2)ϸʵʱٶȺٶȣ

(3)x=0.2mʵt=1sʱλ࣬ԭһʱ̵λ?һλ˶״̬t=1.25sʱ̵һ? : (1)׼ʽ

?

?1?1ȣA?0.05mƵ??5s??0.5mu????2.5m?s

(2)ϸ٣ٶȷֱΪ

y?Acos(2??t?2?x)vmax??A?10??0.05?0.5?m?s?1 amax??2A?(10?)2?0.05?5?2m?s?2 (3)x?0.2m񶯱ԭʱΪ x0.2??0.08s u2.5t?1?0.08?0.92sʱλ࣬

x?0.2m,t?1sʱλԭ(x?0)0 ??9.2У

һλ˶״̬t?1.25sʱ̵x㣬

9-6һƽҲֱΪ14cmԲιܴǿΪ18.010JmsƵ

-1

Ϊ300 HzΪ300ms (1)ƽܶȺܶ? (2)֮ͬжٲ?

x?x1?u(t?t1)?0.2?2.5(1.25?1.0)?0.825m

-3-2-1

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: (1) I?wu

I10?3w??18.0??6?10?5J?m?3 u300

wmax?2w?1.2?10?4 J?m?3

11uW??V?w?d2??w?d244? (2)

1300?6?10?5???(0.14)2??9.24?10?7J 4300??9-7 S1S2ΪɲԴΪA14S1S2λ೬ǰ2 (1) S1ĺǿȣ

(2) S2ĺǿ

⣺1S1࣬S1Ϊr1ĵ㣬S1S2PλΪ

2????r?(r?)???11?2??4?

2A?A1?A1?0,I?A?0

2S2.S2Ϊr1ĵ㣬S1S2õλ.

?????2?4

2A?A1?A1?2A1,I?A2?4A1

9-89-8ͼʾB㷢ƽᲨBP򴫲B񶯷Ϊy1?2?10?3cos2?t;C㷢ƽᲨCP򴫲C񶯷Ϊy2?2?10?3cos(2?t??)ymƣtsƣBP0.4mCP0.5 m

-1

u=0.2ms

(1)Pʱλ

(2)в񶯷ͬʱP񶯵

*(3)в񶯷ഹֱʱP񶯵 : (1)

?????2?(r2???r2)?0???(?2??1)?2??(CP?BP)

????u 2????(0.5?0.4)?00.2

(CP?BP)

9-8ͼ

(2)P೤棬񶯷ͬ

(3)񶯷ֱλΪ0ʱ񶯹켣ͨ򣬢޵ֱߣ

AP?A1?A2?4?10?3m

ѡ