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NEET PHYSICSWAVEMedium

Question

Two cars moving in opposite directions approach each other with speed of 22 m/s22 \text{ m/s} and 16.5 m/s16.5 \text{ m/s} respectively. The driver of the first car blows a horn having a frequency 400 Hz400 \text{ Hz}. The frequency heard by the driver of the second car is [velocity of sound 340 m/s340 \text{ m/s}]

A

350 Hz350 \text{ Hz}

B

361 Hz361 \text{ Hz}

C

411 Hz411 \text{ Hz}

D

448 Hz448 \text{ Hz}

Step-by-Step Solution

  1. Identify the Doppler Effect Formula: The apparent frequency (ff') heard by an observer when both the source and observer are in relative motion along the line joining them is given by f=f(v±vovvs)f' = f \left( \frac{v \pm v_o}{v \mp v_s} \right), where vv is the velocity of sound in the medium, vov_o is the velocity of the observer, and vsv_s is the velocity of the source .
  2. Determine Signs for Approaching Bodies: Since both cars are moving towards each other, they both contribute to an increase in the apparent frequency.
  • The observer approaching the source means the numerator is (v+vo)(v + v_o).
  • The source approaching the observer means the denominator is (vvs)(v - v_s).
  1. Substitute the Given Values: Given v=340 m/sv = 340 \text{ m/s}, vo=16.5 m/sv_o = 16.5 \text{ m/s} (second car), vs=22 m/sv_s = 22 \text{ m/s} (first car), and f=400 Hzf = 400 \text{ Hz}. f=400(340+16.534022)f' = 400 \left( \frac{340 + 16.5}{340 - 22} \right) f=400(356.5318)f' = 400 \left( \frac{356.5}{318} \right) f=400×1.12107...448.4 Hzf' = 400 \times 1.12107... \approx 448.4 \text{ Hz} Rounding off to the nearest integer, the frequency heard by the driver of the second car is 448 Hz448 \text{ Hz}.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from WAVE. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSWAVEmovingoppositedirectionsapproachrespectively

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