asib1214 one year ago Yelp!!!

1. rvc

@Michele_Laino

2. rvc

3. Michele_Laino

since we have three complete cycles within 4.8 meters, then the wavelength is: 4.8/3=1.6 meters

4. rvc

since we have 3 waves so divide 4.8 by 3 because one wave is equal to wavelength

5. rvc

lol sorry i did not see your post @Michele_Laino

6. Michele_Laino

no worries :) @rvc

7. Michele_Laino

the requested velocity, is: 4.8/6=...meters/seconds

8. Michele_Laino

period is T= 6 /3 =...second frequency f= 1/T =... Hz

9. Michele_Laino

if the velocity of our wave is unchanged, then we can apply this formula: $\Large \lambda f = v$ from which we get: $\Large \lambda = \frac{v}{f} = \frac{{0.8}}{2} = ...meters$

10. asib1214

this is how i did it, i first took the inverse of the Ferquency.....F=1/T which agve me the period

11. Michele_Laino

how did you get 14.5 meters/second

12. Michele_Laino

v=traveled space/time interval= 4.8/6=0.8 m/second

13. Michele_Laino

period is T=6/3= 2 seconds

14. Michele_Laino

I think taht: since within 6 seconds we have three complete waves, then the period is:T=6/3= 2 seconds

15. Michele_Laino

so the corresponding frequency is: f=1/T= 1/2=0.5 Hertz

16. asib1214

when solving for the very first question wavelength.

17. asib1214

i mean second cuz time is given after the wavelength question :(

18. asib1214

so do we assume we don't know the time while solving for wavelength

19. Michele_Laino

as I wrote before, in the last part of the first question, we have to assume that the speed of our wave is the same as before, namely, it is 0.8 m/second

20. asib1214

21. asib1214

@Astrophysics

22. asib1214

23. asib1214

the picture is at the top.

24. Astrophysics

|dw:1435727528455:dw| you can find the amplitude using $Amplitude = \frac{ Distance }{ Frequency }$

25. Astrophysics

They are related.

26. Astrophysics

No, the amplitude here is measured in decibels here. I think you're just confusing it because of the formula/ units but not really sure about what this actually means.

27. Astrophysics

$\lambda = \frac{ v }{ f }$

28. asib1214

can you quickly guide me what to do Please?!?!?!?!

29. Astrophysics

Slow down, ok so we have |dw:1435728513829:dw| so we have 3 complete cycles here, so our wavelength is 4.8/3

30. Astrophysics

$y = A \sin \omega t$ you can use this A here is the amplitude the omega is angular frequency and t is the time period.

31. Astrophysics

$\omega = f 2 \pi$

32. Astrophysics

It's one in the same, math and physics are interrelated...

33. Astrophysics

Lol, no problem, it can get confusing I guess, but I think you just need a decent understanding of what everything means and you will get it, you can try khan academy they have some nice videos on such topics I'm sure

34. rvc

i m extremely sorry @asib1214 i was away from the laptop for a long time. Thanks @Astrophysics :) Sorry once again :)

35. rvc

Do you have the formula for amplitude?

36. rvc

so use the formula :)

37. rvc

The maximum displacement of the particle from the mean position is the amplitude.

38. rvc

:/

39. rvc

v=n lambda

40. rvc

:)

41. rvc

idk :(

42. rvc

43. welshfella

i'll have to look later if you still need it gotta go right now

44. welshfella

there are 3 complete waves in the diagram so one wavelength is 4.8 / 3 m

45. welshfella

well the amplitude is the distance from the equilibrium point to the crest of the wave. I'm not sure if we have enough information ..

46. welshfella

i'll have to check that out.

47. welshfella

A = D/F where D is distance travelled by the wave / frequency F

48. welshfella

I'm a bit rusty with this stuff.

49. welshfella

yes i see hmmm

50. welshfella

1.6 m is correct for the wavelength i'm sure of that

51. welshfella

yea sorry my recall of this stuff is really hazy. one website i visited gave the formula A = D / F so i guess its must be right

52. welshfella

D is distance and F = freqency in cycles per second

53. welshfella

yea sorry i cant be of more help. If i have the time i'll have to revise this stuff - I did it in Physics years back!!

54. Michele_Laino

hint: in order to find the amplitude, you have to measure the distances D and H as below:

55. Michele_Laino

you have to measures the distances H adn D on your drawing, using a scale ruler, then you have to solve this proportion: $\Large D:4.8 = H:x$ where x is the requested amplitude

56. Michele_Laino

so we have: $\Large x = \frac{{4.8 \times H}}{D} = ...$

57. Michele_Laino

what is the distance D? Please measure it with a scale ruler

58. Michele_Laino

how many cm is D? how many cm is H?

59. Michele_Laino

ok! and how many cm is D?

60. Michele_Laino

ok! then if we apply our formula, we get: $\Large x = \frac{{4.8 \times H}}{D} = \frac{{4.8 \times 1}}{{10.5}} = ...meters$

61. Michele_Laino

what is x?

62. Michele_Laino

That's right! better is x=0.457 meters

63. Michele_Laino

it is a proportion

64. Michele_Laino

we have finished, since by means of that proportion, our amplitude, is 0.457 meters

65. Michele_Laino

yes! I am sure.

66. Michele_Laino

yes! since our procedure is correct!

67. Michele_Laino

yes! that's right!

68. Michele_Laino

thanks!

69. rvc

Thanks @Michele_Laino

70. Michele_Laino

:) @rvc

71. asib1214

@Astrophysics A tuning fork with a frequency of 420Hz emits sound with a wavelength of 0.82m in air. If the temperature of the air increases, what will happen to the wavelength and why?

72. Astrophysics
73. asib1214

i understand that the rectangular wave on the left has a positive displacement because it's above the equilibrium and the triangle trough has a negative displacement, the thing that i don't understand here is that, Why Triangle trough DOESN'T have any displacement?!?!?!?!

74. Michele_Laino

1) we have a destructive interference when 2 signals overlap each other and they cancel out each other, namely during that overlapping we have no signal, for example the dark fringes in a interference pattern 2) we have a constructive interference, when 2 signals overlap each other and they reinforce each other, so during that overlapping we have a signal whose intensity is greater than each of both overlapped signal. For example the bright fringes in a interference pattern

75. asib1214

i understand that when two waves interfere with each other, they form a constructive wave, and when two waves with opposite displacement destruct each other!!!

76. Michele_Laino

a destructive interference occurs, when from the overlapping between 2 signals, the resultant signal has a little intensity, less than the intensities of each signal

77. asib1214

When these weird shapes confuse me, like when a triangle interferes with a rectangle :( like how do you figure out if they are going to form a constructive or destructive waves :(

78. Michele_Laino

since the phase shift between the rectangle signal and the triangle signal is 180 degree, namely those signals interfere, each other, with opposite phases

79. Michele_Laino

you have to subtract the y-coordinates of the triangle signal, from the corresponding y-coordinate of the rectangle signal

80. asib1214

oh so since the triangle is flipped to 180 degress, but still how do i know the resultant displacement or what shape will wave form during the collision??!!?1

81. Michele_Laino

as I wrote before, you can get that shape if you subtract the y-coordinates of the triangle signal, from the corresponding y-coordinate of the rectangle signal

82. asib1214

can you please draw a quick drawing?!?!!?!?? :(

83. asib1214

84. Michele_Laino

|dw:1436132812859:dw|

85. Michele_Laino

|dw:1436132987610:dw|

86. asib1214

i'll do the next two question after this example, please check them for me, I Love You!!! :")

87. Michele_Laino

then we have: |dw:1436133042674:dw|

88. asib1214

OMG i'm crying here, Thank you so much, please stick around, i'll do the next two questions on my own. Please check them for me!!!! Thank you!!!!

89. asib1214

wait one quick question here. how do you know the amplitude is 5, can you just assume and make up your own numbers to figureout the resultant displacement.

90. asib1214

i nother words, how do yo know what shape is bigger or smaller :(

91. Michele_Laino

the amplitude A is given by this computation: $A = \frac{{\max value - \min value}}{2}$

92. asib1214

OMG i'm going to ask you a very sily question but how did you come up with 5?!?!?

93. Michele_Laino

I chose those value arbitrarily

94. Michele_Laino

values*

95. asib1214

because the picture didn't give any numbers, so when i'm solving questions on my own, how do i assume the amplitude is 5 and 8 :(

96. asib1214

oh okay, let me try the next two questions and i'll get back to you.....i hope you'll be here!!! :")

97. Michele_Laino

no, you have to measure your numbers using a scale ruler

98. asib1214

ok so in what units???? cm?

99. Michele_Laino

yes!

100. asib1214

ok Thanks you Soooooooooooooooooooooooooooooooooooooooooooooooo MCH!!!! :")

101. asib1214

Love you forever!!! :")

102. Michele_Laino

Thanks!