Martha was leaning out of the window on the second floor of her house and speaking to Steve. Suddenly, her glasses slipped from
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To solve this problem we need to apply the corresponding sound intensity measured from the logarithmic scale. Since in the range of intensities that the human ear can detect without pain there are large differences in the number of figures used on a linear scale, it is usual to use a logarithmic scale. The unit most used in the logarithmic scale is the decibel yes described as
Where,
I = Acoustic intensity in linear scale
= Hearing threshold
The value in decibels is 17dB, then
Using properties of logarithms we have,
Therefore the factor that the intensity of the sound was
We can solve the problem by using the first law of thermodynamics, which states that:
where
is the change in internal energy of the system
Q is the heat absorbed by the system
W is the work done by the system
In our problem, the heat absorbed by the system is Q=+194 kJ, while the work done is W=-120 kJ, where the negative sign means the work is done by the surroundings on the system. Therefore, the variation of internal energy is
where
Q is the heat absorbed by the system
W is the work done by the system
In our problem, the heat absorbed by the system is Q=+194 kJ, while the work done is W=-120 kJ, where the negative sign means the work is done by the surroundings on the system. Therefore, the variation of internal energy is