A car $P$ travelling at $20 \mathrm{~ms}^{-1}$ sounds its horn at a frequency of 400 Hz . Another car $Q$ is travelling behind the first car in the same direction with a velocity $40 \mathrm{~ms}^{-1}$. The frequency heard by the passenger of the car Q is approximately [Take, velocity of sound $=360 \mathrm{~ms}^{-1}$ ]
Select the correct option:
A
514 Hz
B
421 Hz
C
485 Hz
D
471 Hz
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
Sol. $\begin{aligned} f & =f_0\left(\frac{c+v_0}{c+v_s}\right) \\ f & =40\left(\frac{360+40}{360+20}\right) \\ f & =421 \mathrm{~Hz}\end{aligned}$
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