Page 82 - SP015 Past Years PSPM Chapter 6 -14 Ver 2020

PHYSICS PSPM SEM 1 1999 - 2017

12. (a) Speed of propagation of wave is the speed of wave front motion @ speed of wave profile when
propagating.
(b) Vibrational speed of a particle is the speed of the particle when vibrating at equilibrium @ speed of
wave energy transferring.
13. (a) Wave propagation velocity is the velocity of wave profile or velocity of energy propagation.
(b) f = 143.2 Hz
 2
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14. (a)  = rad s (b) k = rad cm (c) v = 1.25 cm s
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 2
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(d) v y = 2.51 cm s (e) y = 2 sin ( t – x) cm
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15. (a) y = 15 × 10 sin (25t – 5x) (b) v y = –1.17 m s
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16. v = 261.8 m s
17. v = 0.02 m s -1
18. (a) Direction of wave is to the left @ to negative x-axis. (b)  = 6.28 m
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19. (a) v = 747.6 cm s (b) v max = 3768 m s
20. y = 0.12 sin (t – 2.5x) or y = 0.12 sin (3.14t – 7.9x) where y and x in m and t in s.
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21. (a) k = 50 rad m or k = 157.1 rad m (b) f = 600 Hz
(c) y = 0.02 sin 50 (24t –x) where y and x in m and t in s.
22. Stationary wave is produced by the superposition of two identical progressive waves but moving
towards each other resulting in a steady waveform or series of uniform loops.
Formation of stationary wave is the superposition of two waves having the same speed, frequency and
amplitude travelling in the opposite direction.
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23. v = 10 m s
24. Distance between two successive nodes = 1.5 m
25. (a) Standing wave or stationary wave (b) y = 12 cos 3x sin 2t
26. Sound intensity is power per unit area.
@ Sound intensity at a point is the rate of sound wave energy per unit area.
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27. The intensity is directly proportional to the square of amplitude  I  A .
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The intensity is inversely proportional to the square of distance  I  .
r 2
28. (a) Sound intensity is inversely proportional to the square of distance from the point source.
(b) If the coil speed is increased, wave propagation speed will remain the same because v =  means
f
wave does not depend on the speed of coil.
29. (c) f o = 81.65 Hz (d) amplitude = 0.03 m (e) y = 0.77 cm
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30. v = 34.2 m s ,  = 0.68 m
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31. v = 160 m s
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32. (a)  = 0.04 kg m (b) T = 0.4 s
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33. (a)  1 = 2.55  10 kg m (b)  2 = 2.66  10 kg m (c) f 2 = 342.8 Hz
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34. v = 9.04 m s
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35. (a)  = 2.64  10 kg m (b)   . 0 625 m (c) f = 1320 Hz
36. d new = 0.5d original
37.  = 0.75 m
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38. (a) y = 2  10 sin (3142t – kx) where y and x are in m and t is in s. (b) T = 157.5 N
39. (b) f o = 107.5 Hz, f 7 = 752.5 Hz
40. (a)  = 0.28 m (b)  = 0.56 m
41. (a) f 1 = 425 Hz, f 3 = 1275 Hz (b) f 2 = 1700 Hz
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42. (b) a’ = 7.64  10 m
)
(c) y  02.0 cos ( 5  x sin 410 t  where y and x are in meter and t is in second

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43.  = 0.195 m
44. (a) Air disturbance causes the air column to vibrate at its natural frequency.
@ The air blown resonates with the natural frequency.
(b) f = 250 Hz
45. f = 850 Hz
46. Doppler effect for sound wave is the apparent change in the frequency of sound as a result of relative
motion between the sound and the source.
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48. f a = 600 Hz, v s = 30 m s
49. f beat = 5 Hz
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