Question

A source that is continuously emitting sound at constant frequency, starts moving away from the detector with initial speed 4 m/s, along the line joining them. The acceleration a of the source is opposite to velocity having value 1 m/ s². If the motion starts at t = 0 s then frequency as recorded by the detector from t = 0 to t = 8s

• A. Remains same
• B. First increases then decreases.
• C. First decreases then increases
• D. Increases for whole duration.

Answer 1

Answer: (D)

Increases for whole duration.

Answer 2

At t = 4 sec. source turns direction of motion and starts moving towards detector.

Fort = 0 to t = 4f = f₀ $\frac{V}{V + V_{s}}$as V_s decreases in this duration, f increases .

For t = 4 to t = 8 f = f₀$\frac{V}{V + V_{s}}$ again f increase as V_s increases.

Thus for whole duration f increases.