If we have a perfect gas of mass density Px kg/m,3, and we assign a velocity U m/s to each differential element, then the mass flow rate is pxU kg/(m2-s). Phusical reasoning then leads to the continuty equation, ∇.(pxU)=-âˆ�pxâˆ�t. (a) Explain in words the phisical interpretation of this wquation. (b) Show that
where M is the total mass of the gas whithin the constant closed surface S, and explain the physical significance of the wquation.
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Engineering Electromagnetics
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