A car sounding a horn of frequency 1000 Hz passes an observer. The ratio of frequencies of the horn noted by the observer before and after passing of the car is 11 : 9. If the speed of sound is v , the speed of the car is

Options

A. `(1)/(10)upsilon`
B. `(1)/(2)upsilon`
C. `(1)/(5)upsilon`
D. `upsilon`

Answer

A

Explanation

`f_("before")=((v)/(v-v_(c)))fandf_("after")=((v)/(v+v_(c)))f`
`(f_("before"))/(f_("after"))=(v+v_(c))/(v-v_(c))implies(11)/(9)=(v+v_(c))/(v-v_(c))`
`implies v_(c)=(v)/(10)`.