1. 20m/s

6 . ,

30m/s; (. 13.5 )

2.

= 0.25 sin0.3 40

x y m t s.

(a) , (b) , (c) , (d) , (e) ,

(f) . (. 0.25, 40rad/s, 0.3 m-1

, 20.9 m, 133 m/s, +x )

3. (a) y x t

x

ymax= 8 cm, = 80 cm, f= 3 Hz, y(0,t)= 0 t= 0. (b)

y x (a) y(x,0)= 0

x= 10 cm.

4. (a) y x t

x

ymax= 8 cm, = 80 cm, f= 3 Hz y(0,t)= ymax, t= 0. (b)

(a). (. y=(0.08m)sin[2(x/0.8)-3t+(/2)], 7.85 m-1

, 2.40 m/s)

5. 5 cm

4 x 10-2

kg/m.

300 W 100 ,

; (. 55,1Hz)

6. x

: ymax= 6 cm, = 8 cm, = 48 cm/s

t= 0 x= 0 -2 cm. (a) , (b)

(c) . (d) t

x= 0 +2 cm; (e)

(d), x

y= 0. (. 0.25 cm-1

, 12 s-1

, -0.34 rad/s, 0.262 s, 1.39

cm).

7. 4 N/m2 5000 Hz.

x= 0 P= 0, t=0. (a) P x= 0, t= 2 x 10-4

s (b)

P x= 0.02 m, t= 0. (. 0 Pa, 3.85 Pa)

8. 75 dB 80 dB.

, (a) ; (b) W/m2;

(. 81.2 dB, 1.316x10-4

W/m2)

9. 50 W.

,

5m

(a) 30 Hz, (b) 400 Hz, (c) 20000 Hz. : =1.2kg/m3,

v=343m/s. (. =112 dB , s=1.48x10-4

m 1.10x10-5

m, 2.20x10-7

m)

10. 3560 m/s

8890 kg/m3. ,

2 atm; (. 1.79x10-4

%)

11. 5 m/s . ,

40 kHz 40.4

kHz. ; (

v= 340 m/s). (.3.3m/s)

12. y. S1

(0,0.1) m S2 (0,-0.1) m.

1650 Hz .

y 5 m S1. (a)

; (b)

; (

u= 343 m/s). (. 6.04 rad, 1.985A).

13.

r1= 1.20 m r2=0.80 m. (a)

. (b)

(20-20000 Hz) ; (. 858,

1715, 2572 Hz, 19.3kHz)

14. 60 cm 50

0.1 g/cm.

20000 Hz; (. 19976 Hz)

15. 2 m .

3 m

. 300 Hz. (a)

; (b)

300 Hz

; ( v=343m/s) (. 3.33 rad, 283 Hz).