Question

A train is moving with a speed of $10 m/s$ towards a platform and blows a horn with frequency $400 Hz$. Find the frequency heard by a passenger standing on the platform. Take speed of sound = $310 m/s$.

• A. 405 Hz
• B. 425 Hz
• C. 380 Hz
• D. 413 Hz

Answer 1

Answer: (D)

413 Hz

Answer 2

The correct option is (D): 413 Hz
$f' = f[\frac{(v-v0)}{(v-vs)}]$
$f' = 400[\frac{(310-0)}{(310-10)}]$
$f' = \frac{4}{3}(310)Hz$
$f' ≃ 413 Hz$