physics

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an automobile is travelling towards you at a speed 25.0m/s. When you measure the frequency of its horn, you obtain a value of 26Hz. If the actual frequency of the horn is known to be 240Hz, calculate speed of sound in air?
answer is 325m/s

  • physics -

    Vs = 25 m/s = Velocity of the source.

    F = 260 Hz(NOT 26Hz).

    Fo = 240 Hz.

    Vr = Velocity of the receiver(person)

    F = (V+Vr)/(V-Vs)*Fo = 260 Hz.
    (V+0)/(V-25)*240 = 260
    240V/(V-25) = 260
    240V = 260V - 6500
    -20V = -6500
    V = 325 m/s.

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