2. Solved Papers
  3. MGIMS WARDHA

MGIMS WARDHA MGIMS WARDHA Solved Paper-2008

  • question_answer
    An engine moving towards a wall with a velocity 50 ms-1 emits a note of 1.2 kHz. Speed of sound in air is 350 ms-1. The frequency of the note after reflection from the wall as heard by the driver of the engine is

    A) 2.4kHz                                  

    B) 0.24kHz

    C) 1.6kHz                                  

    D) 1.2kHz

    Correct Answer: C

    Solution :

    The reflected sound appears to propagate in a direction opposite to that of moving engine. Thus, the source and the observer can be presumed to approach each other with same velocity. \[v'=\frac{v(v+{{v}_{0}})}{(v-{{v}_{s}})}\] \[=v\left( \frac{v+{{v}_{s}}}{v-{{v}_{s}}} \right)\]                               \[[\because {{v}_{0}}={{v}_{s}}]\] \[\Rightarrow \]               \[v'=1.2\left( \frac{350+50}{350-50} \right)\]                 \[=\frac{1.2\times 400}{300}\] \[=1.6\text{ }kHz\]


You need to login to perform this action.
You will be redirected in 3 sec spinner