College Physics (4th Edition)

We can write the continuity equation like this: $\rho~A_1~v_1 = \rho~A_2~v_2$ $A$ is cross-sectional area $v$ is velocity Therefore, the expression $~~A~v~~$ is the volume flow per unit time. Then $~~\rho~A~v~~$ is the mass flow per unit time. The form of the continuity equation shows that the rate of mass flow is conserved. The correct answer is: (a) conservation of mass