Fluid, non-stationary rigid body interaction is a commonly occurring phenomenon seen in many engineering practices. The article offers a new method using laws of classical mechanics for obtaining simplified analytical relations in analysis and optimization tasks without using space time programming methods. In the proposed method the fluid space around the rigid body prisms is divided into two zones, pressure and suction (vacuum). The method is extensively discussed which is further extended for calculation of interaction forces and coefficients for non-stationary perforated plate with a total area of perforations maintained at half the area of the complete flat plate. Experiments were performed for a perforated plate in an Arm-field wind tunnel at a constant speed of 10 m/s. The present work offers analysis and synthesis of specific engineering tasks of energy extraction from fluid in a unique way by making use of external fluid flow over a perforated plate. The fluid is assumed continuous and incompressible.