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JEE Advanced 2013Paper 2
Exam
JEE Advanced
Year
2013
Paper
Paper 2
Subject
Physics
Chapter
Waves and Sound

JEE Advanced 2013 · Paper 2 · Physics · Waves and Sound

Two vehicles, each moving with speed u on the same horizontal...

Two vehicles, each moving with speed u on the same horizontal straight road, are approaching each other. Wind blows along the road with velocity w. One of these vehicles blows a whistle of frequency f1. An observer in the other vehicle hears the frequency of the whistle to be f2. The speed of sound in still air is V. The correct statement (s) is (are) :Two vehicles, each moving with speed u on the same horizontal straight road, are approaching each other. Wind blowsTwo vehicles, each moving with speed u on the same horizontal straight road, are approaching each other. Wind blows

Options

  1. AIf the wind blows from the observer to the source, f2 > f1.
  2. BIf the wind blows from the source to the observer, f2 > f1.
  3. CIf the wind blows from the observer to the source, f2 < f1.
  4. DIf the wind blows from the source to the observer, f2 < f1.

Correct answer

A. If the wind blows from the observer to the source, f2 > f1.

Step-by-step solution

Two vehicles, each moving with speed u on the same horizontal straight road, are approaching each other. Wind blows

If wind blows from source to observer
f2=((v+w)+u(v+w)−u)f1{\text{f}}_{2} = \left(\dfrac{\left(\text{v} + \text{w}\right) + \text{u}}{\left(\text{v} + \text{w}\right) - \text{u}}\right) {\text{f}}_{1}
→f2>f1\to {\text{f}}_{2} > {\text{f}}_{1}
If wind blows from observer to source
Two vehicles, each moving with speed u on the same horizontal straight road, are approaching each other. Wind blows
f2=((v−w)+u(v−w)−u)f1{\text{f}}_{2} = \left(\dfrac{\left(\text{v} - \text{w}\right) + \text{u}}{\left(\text{v} - \text{w}\right) - \text{u}}\right) {\text{f}}_{1}
→f2>f1\to {\text{f}}_{2} > {\text{f}}_{1}
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