Question

1. A car P approaching a crossing at a speed of
10 m/s sounds a horn of frequency 700 Hz
when 40 m in front of the crossing. Speed of
sound in air is 340 m/s. Another car Q is at
rest on a road which is perpendicular to the
road on which car P is reaching the crossing
(see figure). The driver of car Q hears the
sound of the horn of car P when he is 30 m in
front of the crossing. The apparent frequency
heard by the driver of car Q is
40m
Po
Crossing
30 m​

Answer 1

Answer:

Correct option is A)

Explanation:

f′=(V−VsV−V0)f

Where, V= Velocity of sound

            Vo= Velocity of observer

            Vs= Velocity of source

Vs along OS =(20)×cosθ=16 m/s

f′=(330−16330)628 =660Hz

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