A car C blowing a horn of frequency $$650$$ Hz is moving at a speed of $$25$$ $$m/$$$$sec$$ on a straight path CP. A person is standing at a point O at a distance of $$40$$ m perpendicular to CP as shown in figure. When car is $$30$$ m away from P, the apparent frequency of sound as heard by the person is (Vsoud=345$$ $$m/$$$$sec$$$$)

Question

A car C blowing a horn of frequency $$650$$ Hz is moving at a speed of $$25$$ $$m/$$$$sec$$ on a straight path CP. A person is standing at a point O at a distance of $$40$$ m perpendicular to CP as shown in figure. When car is $$30$$ m away from P, the apparent frequency of sound as heard by the person is  (Vsoud=345$$ $$m/$$$$sec$$$$)

Infinity Learn · Accepted Answer

Here the observer is at rest and source is in motion and observer will receive  sound at a component of source velocity.$$OC=302+402=50$$ m ucosθ$$=25cos$$θ$$=25$$×$$CPCO=25$$×$$3050=15$$ $$m/$$$$sec$$ Apparent Frequency $$n1=nVV$$−ucosθ$$=650$$×$$345345$$−$$15=680$$ Hz

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