Suppose that a vessel filled with liquid is moving in a straight line at constant acceleration on the horizontal level as shown in Fig. 3.20. Further consider a minute element of mass m on the liquid surface, where its acceleration is CY, the
forces acting on m are gravity in a vertical downward direction -mg, and the inertial force in the reverse direction to the direction of acceleration -ma. There can be no force component normal to the direction of F, the resultant force of gravity and the inertial forces. Therefore, the pressure must be constant on the plane normal to the direction of F. In other words, this plane identifies the equipressure free surface. When 8 is the angle formed by the free surface and the x direction, the following relation is easily obtained:
This is the same relation as the stationary state.
