Fluid Mechanics

Hydrostatic Pressure

  • If an object is placed in a fluid, the fluid pressure will act upon the entire surface of the area at right angles.
  • This is given by the general formula for stress:
\begin{align} \delta = \frac{F}{A} \end{align}


  • $\delta$ is the Pressure (Pa)
  • F is the force (N)
  • A is the area ($m^{2}$)

Also, the deeper an object is put, the higher the pressure.

  • This is given by:
\begin{equation} P = P_{0} + pgh \end{equation}


  • P is pressure at depth h (Pa)
  • $P_{0}$ is the pressure at the top (Pa)
  • p is the density of the fluid ($kg/m^3$)
  • g is the gravitational acceleration $m/s^2$
  • h is the depth below the top (m)
  • Neoprene is a suitable material for the hydraulic stoppers as it is resistant to grease and oil. It is also sufficiently flexible to make a good seal under pressure.