A train standing at the outer signal of a railway station blows a whistle of frequency 400Hz in still air. The train begins to move with a speed of `10ms^(-1)` towards the platform. What is the frequency of the sound for an observer standing on the platform ? (sound velocity in air `=330ms^(-1))`

Explanation

To solve the problem of finding the frequency of the sound for an observer standing on the platform when a train moves towards it, we will use the Doppler effect formula. Here’s a step-by-step solution:

### Step 1: Identify the given values
- Frequency of the whistle (f) = 400 Hz
- Speed of the train (source) (v_s) = 10 m/s (towards the observer)
- Speed of sound in air (v) = 330 m/s
- Speed of the observer (v_o) = 0 m/s (the observer is stationary)

...