1.

A soldier fires a bullet towards a fort-wall and hears the first echo after 2s. He moves a distance of 85m towards the wall, fires a bullet and hears the echo after 1.5 s. The velocity of sound isA. 330 m/sB. 340 m/sC. 345 m/sD. none

Answer» Correct Answer - B
`2x = vt_(1) = 2v`...(i)
`2x -2 xx 85 = v t_(2) = 1.5 v`...(ii)
Subtract equation (ii) from (i),
`2 xx 85 = v(2-1.5)`
`:. 5v = 2 xx 85`
`v = (2 xx 85)/(0.5) = 4 xx 85`
`v = 320 m//s`


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