A fire engine approaches a wall at 5 m/s while the siren emits a tone of 500 Hz frequency. At the time, the speed of sound in air is 340 m/s. How many beats per second do the people on the fire engine hear

The  values is  

Explanation:

From the question we are told that

   The  speed of the fire engine is  

    The frequency of the tone is  

    The speed of sound in air is

The  beat frequency is mathematically represented as

Where   is the frequency of sound heard by the people in the fire engine and is is mathematically evaluated as

substituting values

Thus  

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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