मैक संख्या (Mach number) को किन दो भौतिक राशियों के अनुपात के रूप में परिभाषित किया गया है?

The ratio of the specific weight of a liquid to the specific weight of a standard fluid is known as:

The magnitude of the buoyant force depends on the _____________.

In incompressible fluid dynamics, the continuity equation is ∂u/∂x + ∂v/∂y + ∂w/∂z = 0. What physical law does this equation represent?