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Question Number 41962 by Necxx last updated on 16/Aug/18
A student holding a 324Hz tuning  fork approaches a wall at a speed  of 6ms^(−1) .The speed of sound in air  is 336ms^(−1) .What frequency will  the student detect from waves  omitted from the fork and waves  coming from the wall?
$${A}\:{student}\:{holding}\:{a}\:\mathrm{324}{Hz}\:{tuning} \\ $$$${fork}\:{approaches}\:{a}\:{wall}\:{at}\:{a}\:{speed} \\ $$$${of}\:\mathrm{6}{ms}^{−\mathrm{1}} .{The}\:{speed}\:{of}\:{sound}\:{in}\:{air} \\ $$$${is}\:\mathrm{336}{ms}^{−\mathrm{1}} .{What}\:{frequency}\:{will} \\ $$$${the}\:{student}\:{detect}\:{from}\:{waves} \\ $$$${omitted}\:{from}\:{the}\:{fork}\:{and}\:{waves} \\ $$$${coming}\:{from}\:{the}\:{wall}? \\ $$
Commented by tanmay.chaudhury50@gmail.com last updated on 16/Aug/18
Answered by tanmay.chaudhury50@gmail.com last updated on 16/Aug/18
here observer holding the tuning fork...  that means source of sound and observer  are moving with same velocity...  i am trying to solve it...  1)frequency 324Hz will be heard by the students  omittex from tuning fork...  2)for second part assume the reflected sound  is the source of sound...  taking reference from attached comments  f=(((c±v_r )/(c±v_s )))f_0    f  =(((336+6)/(336−6)))324=335.78≈336  pls check and comment...
$${here}\:{observer}\:{holding}\:{the}\:{tuning}\:{fork}… \\ $$$${that}\:{means}\:{source}\:{of}\:{sound}\:{and}\:{observer} \\ $$$${are}\:{moving}\:{with}\:{same}\:{velocity}… \\ $$$${i}\:{am}\:{trying}\:{to}\:{solve}\:{it}… \\ $$$$\left.\mathrm{1}\right){frequency}\:\mathrm{324}{Hz}\:{will}\:{be}\:{heard}\:{by}\:{the}\:{students} \\ $$$${omittex}\:{from}\:{tuning}\:{fork}… \\ $$$$\left.\mathrm{2}\right){for}\:{second}\:{part}\:{assume}\:{the}\:{reflected}\:{sound} \\ $$$${is}\:{the}\:{source}\:{of}\:{sound}… \\ $$$${taking}\:{reference}\:{from}\:{attached}\:{comments} \\ $$$${f}=\left(\frac{{c}\pm{v}_{{r}} }{{c}\pm{v}_{{s}} }\right){f}_{\mathrm{0}} \\ $$$$\:{f}\:\:=\left(\frac{\mathrm{336}+\mathrm{6}}{\mathrm{336}−\mathrm{6}}\right)\mathrm{324}=\mathrm{335}.\mathrm{78}\approx\mathrm{336} \\ $$$${pls}\:{check}\:{and}\:{comment}… \\ $$
Commented by Necxx last updated on 17/Aug/18
yes sir.This is the answer.Thank  you for your help at all times.
$${yes}\:{sir}.{This}\:{is}\:{the}\:{answer}.{Thank} \\ $$$${you}\:{for}\:{your}\:{help}\:{at}\:{all}\:{times}. \\ $$

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