Fluid Dynamics

Taken from Feynman Lectures Volume II Chapters 40, 41.

Hydrostatics §

• theory of liquids at rest
• no shear forces, thus
• law of hydrostatics: all stresses are normal to any surface inside the fluid

Pressure §

• normal force per unit area is pressure
• pressure stress is same in all directions

Pressure may vary as a function of position, ex. fluid at earth’s surface $p\propto h\propto mg$ as shown below. If density $\rho$ is constant, then

$$p(h)=p(0)-\rho gh.$$