ExamBro
ExamBro
JEE Mains · Physics · STD 11 - Waves and sound
  • JEE Mains 2021
  • Easy
  • Numerical

The frequency of a car horn encountered a change from \(400\, {Hz}\) to \(500\, {Hz}\), when the car approaches a vertical wall. If the speed of sound is \(330\, {m} / {s}\). Then the speed of car is \(.....\,{km} / {h} .\)

Pick an option to check your answer.
Verified Solution

Answer & Solution

Correct Answer

(B) \(132\)

Step-by-step Solution

Detailed explanation

Wall as an observer

Frequency received by wall

\({f}_{1}={f}_{0}\left(\frac{{C}}{{C}-{V}}\right)\)

Again wall as a source

Frequency received by observer on car

\({f}_{2}={f}_{1}\left(\frac{{C}+{V}}{{C}}\right)\)

\(500=400\left(\frac{{C}+{v}}{{C}-{V}}\right)\)

\(\frac{5}{4}=\frac{{C}+{V}}{{C}-{V}}\)

\({C}=9 {V}\)

\({V}=\frac{{C}}{9}=\frac{330}{9}\,{m} / {s}\)

\({V}=\frac{330}{9} \times \frac{18}{5}=132\, {km} / {hr}\)

Same subject
Explore more questions on app