Question

A car approaching a crossing at a speed of
20 m/s sounds a horn of frequency 628 Hz
when 80m from the crossing. The apparent
frequency heard by an observer 60m from
the crossing on the straight road which
crosses the road at right angles is (velocity
of sound=330 m/s)
(1) 660 Hz (2) 680 Hz (3) 640 Hz (4)690 Hz​

Answer 1

Answer:

(1)

Explanation:

f ′ ={(V-Vo)÷(V-Vs)}f

Where, V= Velocity of sound

Vo = Velocity of observer

V s = Velocity of source

Vs along OS = (20)×cosθ=16 m/s

f ` = (330÷330-16) 628 = 660Hz