Assume that, when we walk, in addition to a fluctuating vertical force, we exert a periodic lateral force of amplitude 25 NN at a frequency of about 1 HzHz. Given that the mass of the bridge is about 2000 kgkg per linear meter, how many people were walking along the 144-mm-long central span of the bridge at one time, when an oscillation amplitude of 75 was observed in that section of the bridge

Complete Question

The complete question is shown on the first uploaded image

Explanation:

From the question we are told

   The amplitude of the lateral  force is  

   The frequency is  

   The mass of the bridge per unit length is  

    The length of the central span is  

     The oscillation amplitude of the section  considered at the time considered is  

      The time taken for the undriven oscillation to decay to  of its original value is  t = 6T

Generally the mass of the section considered is mathematically represented as

=>        

=>        

Generally the oscillation amplitude of the section after a  time period  t is mathematically represented as

Here b is the damping constant and the is the amplitude of the section when it was undriven

So from the question  

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=>          

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Generally the amplitude of the section considered is mathematically represented as

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the first, second, and fifth options

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