A detector is revolving in a horizontal circle of radius R = 2.5 m with the help of a massless string as shown in figure with speed 10 m/sec. Source S is emitting sound of frequency 660 Hz and sound v

Question

A detector is revolving in a horizontal circle of radius $R = 2.5 m$ with the help of a massless string as shown in figure with speed 10 m/sec. Source S is emitting sound of frequency 660 Hz and sound velocity in air is $330 m / sec$ . If detector detects a frequency of 680 Hz , then value of x is :-(Angle $θ$ in the figure is measured from the vertical.)

TestHub · Accepted Answer

Ans (B) n ′ = ( v − v s ​ v − v 0 ​ ​ ) n 0 ​ , n ′ = 680 Hz, v s ​ = 0 ∴ 680 = 330 330 + 10 c o s α ​ × 660 ∴ 680 = 660 + 20 cos α ⇒ cos α = 1 ⇒ α = 0 ∘ ∴ x R ​ = cos 6 0 ∘ = 2 1 ​ ⇒ x = 2 R = 5 m

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