How much of the reflected sound is heard by person A?

[Helly123]

Homework Statement

2. Homework Equations
Doppler's Equation

The Attempt at a Solution

(1)[/B] freqA = (v sound - vA )/(v sound - v B) . freq B
*v A = 0 (static)
= V/(V - v) . freq B ...Answer : (d)

(2) freq A hear which is reflected sound by D
first find freq D, *v D, v A = 0 (static)
freq D received from B = (v sound - v D) / (v sound + v B) . freq B
freq D = V / (V + v) . Freq B
freq A = (v sound - v A) / (v sound - v D) . freq D
freq A = V / V . freq D
freq A = V / (V + v) . Freq B ...Answer : (c)

(3) can someone give me clue about this one?

(4) freq C = (v sound + v C) / (v sound - v B) . freq B
freq C = (V + v) / V . Freq B... Answer : (a)

(5) freq A which reflected by D
freq D received from B = (v sound + v D) / (v sound - v B) . freq B
freq D = (V + v)/V . freq B
freq A received from D = (v sound - v A)/(v sound - v D). freq D
freq A = (V) / (V - v) . (V + v) / V . freq B
freq A = (V + v) / (V - v) . freq B ...Answer : (e)are the other numbers also in right way?

 

[BvU]

Hello again,

I think you did fine applying the relevant equation you give.

(3) can someone give me clue about this one?

but for (3) you need another relevant equation involving the answers for (1) and (2). Easily found if you google beat frequency.

 

[Helly123]

(3) f beat = absolute (f2 - f1)
F beat = absolute ( f reflected - Aa)
F beat = abs f(V / (V + v) ) - f( V/(V -v) )
F beat = abs fV(V-v) - (V + v) / (V^2 - v^2)
F beat= abs f.V(-2v)/(V^2 - v^2)
F beat = 2Vv / (V^2 - v^2).f

 

[Helly123]

:D