A cr travelling at a speed of 36h^(-1)sounds its horn of frequency 500 Hz . It is heard by the dirver of another car which is travelling behind the frist car in the same directrion with a velocity of 20 ms *s ^(-1) . Another sound is heard by the driver of the secound car after reflection from a bridge ahead . What will be the frequencies of the two sounds heards heard by the drive of theSound travels in air with a speed of340 m * S(-1) .

A cr travelling at a speed of 36h^(-1)sounds its horn of frequency 500

1.	A cr travelling at a speed of 36h^(-1)sounds its horn of frequency 500 Hz . It is heard by the dirver of another car which is travelling behind the frist car in the same directrion with a velocity of 20 ms s ^(-1) . Another sound is heard by the driver of the secound car after reflection from a bridge ahead . What will be the frequencies of the two sounds heards heard by the drive of theSound travels in air with a speed of340 m S(-1) .
Answer» Solution :The drive of the secund car O is the listener . The frist car 5 and its image S. DUE to reflection on the BRIDGE ahead are two sources of sound . The direction of motion of O to torwerds S and S. So velocity of the listener ,` u_(0) = _ 20 m* S^(-1)` Here , S is receging from O . So velocity of the source S ` `u_(s) = - 36 km * h^(-1)` ` = - (36 xx1000)/(60xx60) m * s^(-1) = - 10m * s^(-1)` . ` therefore ` APPARENT frequency to the listener due to S, ` n. = (V + u_(o)) /( V - u_(2)) xxn ` ` = (340 + 20) /(340 - (-10)) xx 500` ` (360)/(350) xx 500 = 514.3 Hz ` On the other hend , S. is approaching O . So, velocity of the source S. , ` u_(s) = + 10* s^(-1)` ` therefore ` Apparent frequency to the listener due to S. ` n. = (V + u_(0))/(V - u_(s)) xx n = (340 + 20)/(340 - 10) xx 500 ` ` = (360)/(330) xx 500 = 545.5 Hz ` So the driver of the secund car will hear the sounds of frequencies 514.3 Hz and545.5 Hz .