Hearing the siren of an approaching fire truck, you pull over to the side of the road and stop. As the truck approaches, you hear a tone of

Question

Hearing the siren of an approaching fire truck, you pull over to the side of the road and stop. As the truck approaches, you hear a tone of 470 Hz ; as the truck recedes, you hear a tone of 400 Hz .Howmuch time will it take for the truck to get from your position to the fire 5.0 km away, assuming it maintainsa constant speed?

in progress 0
Amity 3 years 2021-08-28T17:34:58+00:00 1 Answers 1 views 0

Answers ( )

  1. Nick
    0
    2021-08-28T17:36:29+00:00
    Reply

    Answer:

    time = 182.68 s

    Explanation:

    given data

    truck approaches = 470 Hz

    truck recedes =  400 Hz

    position away =  5.0 km

    solution

    if V is the speed of sound in air and v is the speed to truck

    f is the frequency of sound

    when truck approach

    f1 = \frac{V+v}{V} f  

    and when truck recede

    f2 = \frac{V+v}{V} f  

    so here we can say

    \frac{f1}{f2} = \frac{V+v}{V-v}   ………..1

    \frac{470}{400} = \frac{340.278+v}{340.278-v}  

    v = 27.37 m/s

    so here 5 km

    S = u×t  + 0.5 ×a×t²  ………..2

    5 × 10³ = 27.37 t + 0

    t = 182.68 s

Leave an answer

Browse

Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )