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PHYSICS, M3 EQ-Bank 2

The diagram shows two rectangular pulses moving along a string, each travelling at a constant speed of 1 cm/s at time  \(t=0\ \text{s}\).

Sketch the appearance of the string at  \(t=2\ \text{s}\)  in the grid below.   (2 marks)
 

 

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PHYSICS, M3 2018 VCE 11

The diagram shows two speakers, \(\text{A}\) and \(\text{ B}\), facing each other. The speakers are connected to the same signal generator/amplifier and the speakers are simultaneously producing the same 340 Hz sound.
 

Take the speed of sound to be 340 ms\( ^{-1}\).

  1. Calculate the wavelength of the sound.   (1 mark)

  2. A student stands in the centre, equidistant from speakers \(\text{A}\) and \(\text{B}\). He then moves towards speaker \(\text{B}\) and experiences a sequence of loud and quiet regions. He stops at the second region of quietness.
  3. How far has the student moved from the centre? Explain your reasoning.   (3 marks)

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a.     \(\lambda=1\ \text{m}\)

b.   Distance moved from the centre:

  • At the centre of the speakers, there is an area of relative loudness
  • This is due to a path difference of 0 metres between the wavelengths of sounds coming from both speaker \(\text{A}\) and speaker \(\text{B}\). 
  • As the student moves towards speaker \(\text{B}\), the two sound waves will experience constructive and destructive interference.
  • The peak of speaker \(\text{A}\) will move into the trough of speaker \(\text{B}\) where he experiences the first region of quietness (node) which is 1 quarter wavelength (0.25m) from the centre.
  • The second region of quietness (node) will be half of a wavelength (0.5m) from the first region of quietness. Thus, the total distance from the centre to the second region of quietness is 0.75m.
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a.    \(\lambda=\dfrac{v}{f}=\dfrac{340}{340}=1\ \text{m}\)

  
b.   Distance moved from the centre:

  • At the centre of the speakers, there is an area of relative loudness
  • This is due to a path difference of 0 metres between the wavelengths of sounds coming from both speaker \(\text{A}\) and speaker \(\text{B}\). 
  • As the student moves towards speaker \(\text{B}\), the two sound waves will experience constructive and destructive interference.
  • The peak of speaker \(\text{A}\) will move into the trough of speaker \(\text{B}\) where he experiences the first region of quietness (node) which is 1 quarter wavelength (0.25m) from the centre.
  • The second region of quietness (node) will be half of a wavelength (0.5m) from the first region of quietness. Thus, the total distance from the centre to the second region of quietness is 0.75m.
♦♦♦ Mean mark (b) 20%.