A person standing in front of a vertical cliff fires a gun and hears its echo in 3 s. The speed of sound in air is 340 m/s:

If the speed of sound changes to 350 m/s then how much distance should the person move towards or away from the cliff in order to hear the echo in the same time. Steps are given to calculate the distance. Select the correct sequence of the steps from the given option.
(i) `(340 + 350)/( 2) = ( 2d)/(3)`
(ii) `350- 340 = ( 2d)/(3)`
(iii) `d = ( 345xx 3)/( 2) = 517.5`m
(iv) `d = ( 30)/(2) = 15` m
(v) `7.5` m

Options

A. (ii), (iii) then (v)
B. (iv) then (ii)
C. (iv) then (v)
D. (ii) then (iv)

Answer

D

Explanation

Explanation: if `v = 350" m/sec"`
`d = ?`
for `t = 3" sec"`
Change in velocity `= ( 2d)/(t)`
`350 - 340 = ( 2d)/( 3" sec")`
`d = (30)/(2) = 15" m"`