Physics Circle home Student Login

Home›Chapters›Wave Motion PYQs›Doppler Effect›Question 19

MHT CET 2025 (21 Apr, Shift 2) · Doppler Effect

Doppler Effect question from MHT CET 2025 (21 Apr, Shift 2)

Q19MHT CET 2025 · 21 APR · SHIFT 2Difficult

Doppler Effect

A vehicle starts from rest and accelerates along straight path at 2 m/s22\text{ m/s}^2. At the starting point of the vehicle, there is a stationary electric siren. How far has the vehicle nearly gone when the driver hears the siren at 94%94\% of its value when the vehicle was at rest?

(speed of sound =330 m/s= 330\text{ m/s})

Show answer and solution

Answer: (a)

  1. Observer moving away from a stationary source: f′=fv−uvf' = f\frac{v-u}{v}
  2. 0.94=330−u330⇒u=0.06×330=19.80.94 = \frac{330 - u}{330} \Rightarrow u = 0.06 \times 330 = 19.8 m/s
  3. From rest: s=u22a=(19.8)22×2≈98s = \frac{u^2}{2a} = \frac{(19.8)^2}{2 \times 2} \approx 98 m
  4. So the answer is (a) 98 m.
Report a mistake

More questions on Doppler Effect