InterviewSolution
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InterviewSolution
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A stationary source is emitting sound at a fixed frequency `f_(0)`, which is reflected by two cars approaching the source. The difference between the frequencies of sound reflected from the cars is `1.2%` of `f_(0)`. What is the difference in the speeds of the cars (in km per hour) to the nearest integer ? The cars are moving at constant speeds much smaller than the speed of sound which is `330 ms^(-1)`.A. 2B. 3C. 5D. 7 |
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Answer» Correct Answer - D `f_(app)=f_(0)""(c+v )/(c-v)` , where `c` is speed of sound `rArr" "df=(2f_(0)c)/((c-v)^(2))dv~~(2f_(0)c)/((c-v)^(2))dv=(2f_(0))/(c)dv" "`...(i) Given : `df=(1.2)/(100)f_(0) " "`...(ii) From eqs. (i) and (ii), `dv ~~2m//s=7km//h` |
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