Question

What does the conservation of mass principle state for a fluid in motion?

• A. Mass is transferred from high to low pressure areas.
• B. The mass of fluid leaving a system equals the mass entering.
• C. Mass can be converted into energy.
• D. Mass increases with velocity.

Hint:

Conservation of Mass (Continuity). For steady fluid flow, the mass flow rate entering a control volume equals the mass flow rate leaving it. \( \rho_1 A_1 V_1 = \rho_2 A_2 V_2 \). If incompressible (\(\rho_1=\rho_2\)), then Volume flow rate is conserved: \( A_1 V_1 = A_2 V_2 \).

Answer 1

The Correct Option is B

The principle of conservation of mass, applied to fluid dynamics (often via the continuity equation), states that mass cannot be created or destroyed.
For a steady flow through a control volume or system, this implies that the rate at which mass enters the system must equal the rate at which mass leaves the system.
In simpler terms, what goes in must come out (mass-wise) if there's no accumulation within the system.
Option (2) accurately reflects this principle for steady flow.
Option (1) describes pressure-driven flow.
Options (3) and (4) relate to relativistic physics, not standard fluid mechanics mass conservation.