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JEE Main & Advanced JEE Main Paper (Held on 10-4-2019 Morning)

  • question_answer
    A stationary source emits sound waves of frequency 500 Hz. Two observers moving along a line passing through the source detect sound to be of frequencies 480 Hz and 530 Hz. Their respective speeds are, in \[m{{s}^{-1}},\]
    (Given speed of sound = 300 m/s)
    [JEE Main 10-4-2019 Morning]

    A) 16, 14             

    B) 12, 18

    C) 12, 16             

    D) 8, 18

    Correct Answer: B

    Solution :

    \[f=480=\frac{300-{{\text{v}}_{1}}}{300}\times 500\]           \[\frac{1440}{5}=300-{{\text{v}}_{1}}\]           \[{{\text{v}}_{1}}=\frac{60}{5}=12m/s\]           \[530=\frac{300+{{\text{v}}_{2}}}{300}\times 500\]           \[1590=1500+5{{\text{v}}_{2}}\]           \[5{{\text{v}}_{2}}=90\] \[{{\text{v}}_{2}}=18m/s\]


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