Fluid Dynamics (Bernoulli, Continuity, Flow Rate) — A/L Physics

Steady (Laminar) Flow Flow where every fluid particle passing a given point follows the same path, with velocity constant in time at any point. In steady flow, streamlines do not cross, and the fluid moves in smooth layers. This idealisation allows us to apply the continuity equation and Bernoulli’s principle. Real fluids may become turbulent at high speeds, but laminar flow is assumed in A/L problems unless stated otherwise.

Equation of Continuity For an incompressible fluid flowing through a pipe of varying cross-section, the product of cross-sectional area and flow speed is constant. This arises from conservation of mass: what flows in must flow out. If the pipe narrows, the fluid must speed up to maintain the same volume flow rate. Example: water from a garden hose speeds up when you partially cover the nozzle.