A man is driving a vechicle at 36 km/hr on a straight road towards a hill. He sounds the horn and hears its echo after 4s At what distance from the hill was the horn sounded ? (Velocity of sound = 340 ms)

Options

A. 680 m
B. 700 m
C. 720 m
D. 350 m

Answer

B

Explanation

`v = 36 xx (5)/(18) = 10 m//s`
`v_(s) = (2x - v_(p)t)/(t)`
`2x - v_(p)t = v_(s)t = 340 xx 4`
`2x = 1360 + 10 xx 4 = 1360 + 40`
`2x = 1400`
`x = 700 m`