Question

Two trains A and B are moving in the same direction with velocities 30 m/s and 10 m/s respectively. B is behind from A and A blows a horm of frequency 450 Hz. Then the apparent frequency heard by observer on train B is (speed of sound is 330 m/s):

Answer 1

the apparent frequency is 30/(30-10)×450
i.e.,875hz

Answer 2

Apparent Frequency heard by observer on train B are 425.025 Hz (approaching) and 480.015 Hz (receding)

Explanation:

Given data

Velocity of the train A   ($v_{S}$)      = 30 meter per second

Velocity of the train B     ($v_{l}$)     = 10 meter per second  

Frequency of the horn    ($n_{a}$)   =   450 Hz  

Speed of the sound     (v)         =  330 meter per second

To find - Apparent Frequency heard by observer on train B

Apparent Frequency is a frequency heard by an observer in rest or motion.

It may or may not similar to the actual frequency

Apparent Frequency =  ((v+ $v_{l}$) ÷ ( v + $v_{S}$)) $n_{a}$

(when observer approaching the source)

Apparent Frequency = (( 330 + 10) ÷ (330 + 30)) 450

Apparent Frequency = (340 ÷ 360) 450

Apparent Frequency  = 0.9445 × 450

Apparent Frequency = 425.025 Hz

Apparent Frequency = (( v- $v_{l}$ ) ÷ (v - $v_{S}$ )) $n_{a}$

(when the observer receding the source)

Apparent Frequency = ((330 - 10) ÷ (330 - 30)) 450

Apparent Frequency = (320 ÷ 300) 450

Apparent Frequency = 1.0667 × 450

Apparent Frequency = 480.015 Hz

To Learn More

1. https://brainly.in/question/7709227

2. https://brainly.in/question/8734112