What happens when you pluck a guitar string? A. The string stops air molecules from vibrating.
B. The string vibrates and makes a sound.
C. The string makes a column of air longer.
D. The string echoes.

Ahe-xe mixture containing a 0.75 mole fraction of helium is used for cooling electronics in an avionics application. at a temperature of 300 k and atmospheric pressure, calculate the mass fraction of helium and the mass density, molar concentration and molecular weight of the mixture. if the cooling capacity is 10 l, what is the mass of the coolant?

What is the heat treatment of metals? what is the benefit of it? why and how it's useful? answer in details, do not write by hand.

Avolume of 2.65 m3 of air in a rigid, insulated container fitted with a paddle wheel is initially at 264 k, 5.6 bar. the air receives 432 kj by work from the paddle wheel. assuming the ideal gas model with cv = 0.71 kj/kg • k, determine for the air the amount of entropy produced, in kj/k