Two cars are approaching each other at an equal speed of 7.2 km/hr. When they see each other, both blow horns of 676Hz. The beat frequency heard by each driver will be…………………. Hz.

[Velocity of sound in air is 340 m/s]

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1 Answer

Answered by

Vishal Baghel | Contributor-Level 10

2 months ago

$7.2 \times \frac{5}{18} = 2 m / s$ [V_A = V_B = 2m/s]

$f'_{B} = f_{A} (\frac{v + v_{B}}{v - v_{A}})$

$↓$

App freq heard by car B

$f'_{B} = 676 [\frac{340 + 2}{340 - 2}] = 676 \times \frac{342}{338} = 684 H z$

Similarly, $f'_{A} = f_{B} (\frac{v + v_{B}}{v - v_{B}}) = 684 H z$

$∴$ Beat frequency heard by both = 684 – 676 = 8Hz

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