A source of sound S is travelling at $$100/3$$ $$m/s$$ along a road, towards a point A. When the source is $$3$$ m away from A, a person standing at a point O on a road perpendicular to AS hears a sound of frequency v'. The distance of O from A at that time is $$4$$ m. If the original frequency is $$640$$ Hz, then the value of v' is (velocity$$ of sound is $$340$$ $$m/s)

Question

A source of sound S is travelling at $$100/3$$ $$m/s$$ along a road, towards a point A. When the source is $$3$$ m away from A, a person standing at a point O on a road perpendicular to AS hears a sound of frequency v'. The distance of O from A at that time is $$4$$ m. If the original frequency is $$640$$ Hz, then the value of v' is (velocity$$ of sound is $$340$$ $$m/s)

Infinity Learn · Accepted Answer

Effective value of velocity of source $$isvs=1003cos$$θ⇒$$=1003$$×$$35=20$$ $$m/s$$⇒v'$$=vv$$−vsv⇒v'$$=340340$$−$$20$$×$$640$$ $$Hz=680$$ Hz

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