Question

During an unsteady-flow process:
Select one:
a. The amount of mass entering a control volume is the double of the amount of mass leaving.
b. The amount of mass entering a control volume have to be equal to the amount of mass leaving.
c. The amount of mass entering a control volume does not have to be equal to the amount of mass leaving.

Answer 1

In a control volume,if the mass flow rate entering and leaving are different,it implies that mass in the control volume is changing with time,this type of flow called unsteady flow process.

It is not necessary that mass entering is the double of mass leaving the control volume.
So option b is inappropriate.

Expamle of unsteady flow process is charging or discharging a tank.

Option (c) is correct option for this question.

On the other hand if mass flow rate of entering and leaving are equal thus this type of flow called steady flow process. In this case there will be no Change in mass fluid in the control volume.(option b)

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