You are given information on the intensity level (which is a measure of the sound intensity) at a point and its distance from the sound source. to make use of this information, you will need to determine the relation between sound intensity and distance from the source. which of the following statements correctly expresses that relation?
a) the intensity at any distance r is directly proportional to r.
b) the intensity at any distance r is directly proportional to r^2.
c) the intensity at any distance r is inversely proportional to r.
d) the intensity at any distance r is inversely proportional to r^2.
e) the square of the intensity at any distance r is directly proportional to r.
f) the square of the intensity at any distance r is inversely proportional to r.

As part of an industrial process, air as an ideal gas at 10 bar, 400k expands at steady state through a valve to a pressure of 4 bar. the mass flow rate of air is 0.5 kg/s. the air then passes through a heat exchanger where it is cooled to a temperature of 295k with negligible change in pressure. the valve can be modeled as a throttling process, and kinetic and potential energy effects can be neglected. (a) for a control volume enclosing the valve and heat exchanger and enough of the local surroundings that the heat transfer occurs at the ambient temperature of 295 k, determine the rate of entropy production, in kw/k. (b) if the expansion valve were replaced by an adiabatic turbine operating isentropically, what would be the entropy production? compare the results of parts (a) and (b) and discuss.

Which of the following are appropriate acceleration units?

Calculate 9 ∙ 10-5 divided by 3 ∙ 10-9. (box after the "10" in answer is for the