If man were standing unsymmetrically between parallel cliffs, claps his hands and starts hearing a series of echoes at intervals of 1 s. If speed of sound in air is 340 ms-1, the distance between two cliffs would be ......

If man were standing unsymmetrically between parallel cliffs, claps hi

1.	If man were standing unsymmetrically between parallel cliffs, claps his hands and starts hearing a series of echoes at intervals of 1 s. If speed of sound in air is 340 ms-1, the distance between two cliffs would be ......
Answer» (A) 340 m (B) 510 m (C) 170 m (D) 680 m SOLUTION : Here distance between two CLIFFS is supppose d which is equal to x + y. Suppose `x lt y` Here when sound is produced from position S at time `t =0,` first echo is heard at time `t_(1) -0= t _(1)=1s` (as per statement) as SECONS echo is heard at time `t _(2) -0 =t _(2) =t _(1) +1 (because` successive echose are heard at an INTERVAL of 1 s and so ` t _(2) -t_(1) = 1s)` Now, `2x =vt _(2)` `2y = vt _(2)` `therefore 2x + 2y =v (t _(1) + t _(2))` `therefore 2 (c + y ) = v (t _(1) + y _(2))` `therefore 2d = v (t _(1) + t _(2))` `therefore d = (v (t _(1) + t _(2)))/( 2) = (340 (1+2))/( 2) = 510 m`