- #1

Frozen_Mind

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**1. The problem statement**

1) A train whistle has a frequency of 1000 Hz. If the train is speeding

at a velocity of 60 km/h past a stationary railroad crossing

attendant, what is the apparent frequency a) as the train approaches him, b) as it moves away from him?

Assume speed of sound to be 350 m/s.

2) A second train is approaching the first train (above) with a speed of

60 km/h. Obtain the frequency of the whistle of the first as heard by

the engineer of the second train.

3) Sound is reflected by a screen moving with a speed 20 km/h toward

the source and observer. If the frequency of the source is 450 khz,

what is the apparent frequency of the reflected sound?

## Homework Equations

f2 = f1Vs/(Vs + or - Vo), f2 = f1(1 + or - Vo/Vs)

meh I'm really not that quite sure :S

## The Attempt at a Solution

I could calculate number 1 using the doppler effect equation f2 = f1Vs/(Vs + or - Vo), but I'm not quite sure how to solve for number 2 and 3... help please ?