If the pitch of the sound of a source appears to drop by 10% to a moving person, then determine the velocity of motion of the person. Velocity of the sound `=330ms^(-1)`.

Explanation

Apparent frequency heard by the person is given by,
`v'=((v-v_(0))/(v))v`
(or) `(v')/(v)=(v-v_(0))/(v)`
But `(v')/(v)=(90)/(100)=(9)/(10),v=330ms^(-1)`
`:.(9)/(10)=(330-v_(0))/(330)`
(or) `330-v_(0)=(9)/(10)xx330=297`
`:.v_(0)=330-297=33ms^(-1)`
As the pitch of the sound appears to decrease, so the person is moving away from the observer.