Two men are walking along a horizontal straight line in the same direction. The man in front walks at a speed 1.0 `ms^(-1)` and the man behind walks at a speed `2.0 ms^(-1)`. A third mad is standing at a height 12m above the same horizontal line such that all three men are in a vertical plane. The two walking men are blowing identical whistles which emit a sound of frequency 1430 Hz. The speed of sound in air is 330 `ms^(-1)`. At the instant, when the moving men are 10 m apart, the stationary man is equidistant from them. The frequency of beats in Hz, heard by the stationary man at this instant, is

Answer

5 or 5.0 or 5.00

Explanation

`f_1=(f_0c)/(c-2 cos theta)`
`f_2=(f_(0)c)/(c+1 cos theta)`
Beat frequency `=|f_1-f_2|=(f_0c(3 cos theta))/(c^(2))=(1430xx3)/(330)xx5/13=5`