Problem 46P

Two loudspeakers are 1.80m apart. A person stands 3.00m from one speaker and 3.50m from the other. (a) What is the lowest frequency at which destructive interference will occur at this point? (b) Calculate two other frequencies that also result in destructive interference at this point (give the next two highest). Let T = 20°C.

Solution 46PIntroductionWe will calculate the energy released by the body of the seak person. Then we will calculatethe mass of the ice that will be melted using the same energy.SolutionStep 1The energy released by the body of the person is given byQ body= m body bodyT body………….(1)Where m = 60 kg is the mass of the body, C = 3400 J/kg/K is the specific heat of body bodythe body, and T = (40 39) = 1 = 1 K is the change in temperature.Using this value on the above equation, we can get the energy released by the body, which is 5Q body= (60 kg)(3400 J/kg/K)(1 K) = 2.04 × 10 J ………….(2)