Question

Bernoulli's equation is conservation of

• A. Mass
• B. Energy
• C. Momentum
• D. Angular Momentum

Hint:

Look at what each term in Bernoulli's equation, pressure head, velocity head and elevation head, physically represents.

Answer 1

The Correct Option is B

Step 1: Bernoulli's equation for an ideal, incompressible, steady flow along a streamline is written as \(\dfrac{p}{\rho g} + \dfrac{v^2}{2g} + z = constant\).

Step 2: Each term in this equation has units of length (head), and each one represents a form of mechanical energy per unit weight of fluid, pressure energy, kinetic energy, and potential energy.

Step 3: The equation says that as fluid moves along the streamline, this total mechanical energy per unit weight stays the same (no losses due to friction are assumed). That is nothing but the principle of conservation of energy applied to a flowing fluid.

Step 4: Conservation of mass is expressed separately through the continuity equation, and conservation of momentum is expressed through the momentum equation, so those two options do not describe Bernoulli's equation. Angular momentum is not involved at all here.

Step 5: So the correct answer is Energy.