Flow and continuity — The key idea

The key idea

Start with the central idea, then test it against a concrete element or example. A scientific model is useful when we know what it explains — and where its limits are.

Why it matters

For steady flow, conservation of mass constrains how density, cross-sectional area and flow speed vary along a stream tube.

A picture to remember

For an incompressible fluid, narrowing the available area increases the mean flow speed.

The key idea

Start with the central idea, then test it against a concrete element or example. A scientific model is useful when we know what it explains — and where its limits are.

The key idea

For steady flow, conservation of mass constrains how density, cross-sectional area and flow speed vary along a stream tube.