The linear momentum balance for a nondeforming, stationary control volume is

. Since the flow is steady, the momentum balance simplifies to

, where

is velocity,

is the density of the fluid,

represents the product of the component of velocity normal to the control surface, and

is the differential area of the control surface. The velocity coming out of the turbine is determined using the continuity equation for an incompressible fluid,

. The overall force balance takes into account the pressures at the inlet and the outlet.

, where

is the resultant force,

is the intake pressure, and

is fixed at 0 kPa for this Demonstration.