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½â£º½«F = -?2xÓëF = -kx±È½Ï£¬ÖªÖʵã×÷¼òгÕñ¶¯£¬

k= ?2£® k??ÓÖ ?? mm2? T??2m

m0Fx

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11-2 ÖÊÁ¿Îª2 kgµÄÖʵ㣬°´·½³Ìx?0.2sin[5t?(?/6)] (SI)ÑØ×ÅxÖáÕñ¶¯£®Çó£º

(1) t = 0ʱ£¬×÷ÓÃÓÚÖʵãµÄÁ¦µÄ´óС£» (2) ×÷ÓÃÓÚÖʵãµÄÁ¦µÄ×î´óÖµºÍ´ËʱÖʵãµÄλÖã® ½â£º(1) t = 0ʱ£¬ a = 2.5 m/s2 £¬| F | = ma = 5 N (2) | amax | = 5£¬Æäʱ | sin(5t - ?/6) | = 1 | Fmax | = m| amax | = 10 N x = ¡À0.2 m£¨Õñ·ù¶Ëµã£©

11-15 Ò»ÎïÌå×÷¼òгÕñ¶¯£¬ÆäËÙ¶È×î´óÖµvm = 3310-2 m/s£¬ÆäÕñ·ùA = 2310-2 m£®Èôt = 0ʱ£¬ÎïÌåλÓÚÆ½ºâλÖÃÇÒÏòxÖáµÄ¸º·½ÏòÔ˶¯. Çó£º

(1) Õñ¶¯ÖÜÆÚT£» (2) ¼ÓËٶȵÄ×î´óÖµam £» (3) Õñ¶¯·½³ÌµÄÊýֵʽ£®

½â: (1) vm = ?A ¡à? = vm / A =1.5 s-1 ¡à T = 2?/????4.19 s

(2) am = ?2A = vm ?? = 4.5310-2 m/s2

1 (3) ???

21 x = 0.02cos(1.5t??) (SI)

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11-24 Ò»ÎïÌåÖÊÁ¿Îª0.25 kg£¬ÔÚµ¯ÐÔÁ¦×÷ÓÃÏÂ×÷¼òгÕñ¶¯£¬µ¯»ÉµÄ¾¢¶ÈϵÊýk = 25 N2m-1£¬Èç¹ûÆðʼÕñ¶¯Ê±¾ßÓÐÊÆÄÜ0.06 JºÍ¶¯ÄÜ0.02 J£¬Çó (1) Õñ·ù£»

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(2) ¶¯ÄÜÇ¡µÈÓÚÊÆÄÜʱµÄÎ»ÒÆ£»

(3) ¾­¹ýƽºâλÖÃʱÎïÌåµÄËÙ¶È£®

1½â£º(1) E?EK?Ep?kA2

2 A?[2(EK?Ep)/k]1/2= 0.08 m

121kx?mv2 222 m?2x2?m?2A2sin(?t??)

(2)

2 x2?A2sin(?t??)?A2[1?cos2(?t??)]?A2?x2

2x2?A2£¬ x??A/2??0.0566 m (3) ¹ýƽºâµãʱ£¬x = 0£¬´Ëʱ¶¯ÄܵÈÓÚ×ÜÄÜÁ¿

1 E?EK?Ep?mv2

2 v?[2(EK?Ep)/m]1/2??0.8 m/s

11-29 Á½¸öͬ·½Ïò¼òгÕñ¶¯µÄÕñ¶¯·½³Ì·Ö±ðΪ

31 x1?5?10?2cos(10t??) (SI), x2?6?10?2cos(10t??) (SI)

44ÇóºÏÕñ¶¯·½³Ì£®

½â£ºÒÀºÏÕñ¶¯µÄÕñ·ù¼°³õÏ๫ʽ¿ÉµÃ

312?2A1A2co?s??52?62?2?5?6?cos(???)?10?2 m A?A12?A244 ?7.81?10?2 m

5sin3?(/4)?6sin?(/4) ??arctg = 84.8¡ã=1.48 rad

5cos3?(/4)?6cos?(/4)10t?1.48) (SI) ÔòËùÇóµÄºÏ³ÉÕñ¶¯·½³ÌΪ x?7.81?10?2cos(

11-30 Ò»ÎïÌåͬʱ²ÎÓëÁ½¸öͬ·½ÏòµÄ¼òгÕñ¶¯£º x1?0.04cos2?(t?1?) (SI), x2?0.03cos(2?t??) (SI)

2Çó´ËÎïÌåµÄÕñ¶¯·½³Ì£®

½â£ºÉèºÏ³ÉÔ˶¯£¨¼òгÕñ¶¯£©µÄÕñ¶¯·½³ÌΪ x?Acos?(t??)

2?2A1A2cos?2(??1) ¢Ù Ôò A2?A12?A2ÒÔ A1 = 4 cm£¬A2 = 3 cm£¬?2??1???1??1?´úÈë¢Ùʽ£¬µÃ

22 A?42?32cm?5 cm

Asin?1?A2sin?20.04?arctgÓÖ ??arctg1 ¢Ú

A1cos?1?A2cos?2?0.03 ¡Ö127¡ã¡Ö2.22 rad

¡à x?0.05cos(2?t?2.22) (SI)

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12-2 Ò»Æ½Ãæ¼òг²¨ÑØxÖáÕýÏò´«²¥£¬²¨µÄÕñ·ùA = 10 cm£¬²¨µÄ½ÇƵÂÊ? = 7? rad/s.µ±t = 1.0 sʱ£¬x = 10 cm´¦µÄaÖʵãÕýͨ¹ýÆäƽºâλÖÃÏòyÖḺ·½ÏòÔ˶¯£¬¶øx = 20 cm´¦µÄbÖʵãÕýͨ¹ýy = 5.0 cmµãÏòyÖáÕý·½ÏòÔ˶¯£®Éè¸Ã²¨²¨³¤? >10 cm£¬Çó¸ÃÆ½Ãæ²¨µÄ±í´ïʽ£®

½â£ºÉèÆ½Ãæ¼òг²¨µÄ²¨³¤Îª?£¬×ø±êÔ­µã´¦ÖʵãÕñ¶¯³õÏàΪ?£¬Ôò¸ÃÁÐÆ½Ãæ¼òг²¨µÄ±í´ïʽ¿Éд³É y?0.1cos7?(t?2?x/???) (SI) t = 1 sʱ y?0.1cos7?[?2?(0.1/?)??]?0 Òò´ËʱaÖʵãÏòyÖḺ·½ÏòÔ˶¯£¬¹Ê

1? ¢Ù 2¶ø´Ëʱ£¬bÖʵãÕýͨ¹ýy = 0.05 m´¦ÏòyÖáÕý·½ÏòÔ˶¯£¬Ó¦ÓÐ y?0.1cos[7??2?(0.2/?)??]?0.05

1ÇÒ 7??2?(0.2/?)????? ¢Ú

3ÓÉ¢Ù¡¢¢ÚÁ½Ê½ÁªÁ¢µÃ ?? = 0.24 m ???17?/3

7??2?(0.1/?)???¡à ¸ÃÆ½Ãæ¼òг²¨µÄ±í´ïʽΪ

?x17??] (SI) 0.123?x1»ò y?0.1cos[7?t???] (SI)

0.123

12-4 Ò»ÁÐÆ½Ãæ¼òг²¨ÔÚýÖÊÖÐÒÔ²¨ËÙu = 5 m/sÑØy (cm) y?0.1cos[7?t?xÖáÕýÏò´«²¥£¬Ô­µãO´¦ÖÊÔªµÄÕñ¶¯ÇúÏßÈçͼËùʾ£® (1) Çó½â²¢»­³öx = 25 m´¦ÖÊÔªµÄÕñ¶¯ÇúÏߣ® (2) Çó½â²¢»­³öt = 3 sʱµÄ²¨ÐÎÇúÏߣ®

2O24t (s)

½â£º(1) Ô­µãO´¦ÖÊÔªµÄÕñ¶¯·½³ÌΪ

11 y?2?10?2cos(?t??)£¬ (SI)

2211²¨µÄ±í´ïʽΪ y?2?10?2cos(?(t?x/5)??)£¬ (SI)

22 x = 25 m´¦ÖÊÔªµÄÕñ¶¯·½³ÌΪ

1 y?2?10?2cos(?t?3?)£¬ (SI)

2Õñ¶¯ÇúÏß¼ûͼ (a)

(2) t = 3 sʱµÄ²¨ÐÎÇúÏß·½³Ì

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y?2?10?2cos(???x/10)£¬ (SI) ²¨ÐÎÇúÏß¼ûͼ

y (m)2310-2y (m)u510152025x (m)O1234-2310-2t (s)O(a) (b)

12-15 Ò»Æ½Ãæ¼òг²¨£¬ÆµÂÊΪ300 Hz£¬²¨ËÙΪ340 m/s£¬ÔÚ½ØÃæÃæ»ýΪ3.00310-2 m2µÄ¹ÜÄÚ¿ÕÆøÖд«²¥£¬ÈôÔÚ10 sÄÚͨ¹ý½ØÃæµÄÄÜÁ¿Îª2.70310-2 J£¬Çó (1) ͨ¹ý½ØÃæµÄƽ¾ùÄÜÁ÷£» (2) ²¨µÄƽ¾ùÄÜÁ÷Ãܶȣ» (3) ²¨µÄƽ¾ùÄÜÁ¿Ãܶȣ®

½â£º(1) P?W/t?2.70310-3 J/s

(2) I?P/S?9.00310-2 J /(s2m2) (3) I?w?u

­ã w?I/u?2.65310-4 J/m3

12-18 ÈçͼËùʾ£¬Á½Ïà¸É²¨Ô´ÔÚxÖáÉϵÄλÖÃΪ

S1ºÍS2£¬Æä¼ä¾àÀëΪd = 30 m£¬S1λÓÚ×ø±êÔ­µãO£®ÉèO x1 x2 x S1 S2 ²¨Ö»ÑØxÖáÕý¸º·½Ïò´«²¥£¬µ¥¶À´«²¥Ê±Ç¿¶È±£³Ö²»

d ±ä£®x1 = 9 m ºÍx2 = 12 m´¦µÄÁ½µãÊÇÏàÁÚµÄÁ½¸öÒò¸É Éæ¶ø¾²Ö¹µÄµã£®ÇóÁ½²¨µÄ²¨³¤ºÍÁ½²¨Ô´¼ä×îСÏàλ²î£®

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d?x1x]?[?1?2?1]?(2K?1)? [?2?2?

??¼´ (?2??1)?2?d?2x1??(2K?1)? ¢Ù

ÔÚx2µãÁ½²¨ÒýÆðµÄÕñ¶¯Ïàλ²î d?x2x]?[?1?2?2]?(2K?3)? [?2?2???¼´ (?2??1)?2?d?2x2?¢Ú£­¢ÙµÃ 4?(x2?x1)/??2? ??2(x2?x1)?6 m

ÓÉ¢Ù ?2??1?(2K?1)??2??(2K?3)? ¢Ú

d?2x1??(2K?5)?

µ±K = -2¡¢-3ʱÏàλ²î×îС ?2??1???¡£

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