The aim of this practical was to investigate the reality or the accuracy of the formula for the resultant force on and the position of the centre of pressure on a vertical rectangular surface. SKETCH OF APPARATUS Counterbalance weight Balance pan(with 20g mass piece) Flat/curved surface(as shown below) Water Beaker Mass pieces(20g each)
SUMMARY OF THEORY Hydrostatic force is the force exerted by the pressure of a fluid which is at rest on a surface. A fluid which is contact with a solid surface will exert a hydrostatic force in all small area of the surface and this hydrostatic force will be equal to the product p on the element and its area …show more content…
If the solid surface is a plane/flat surface therefore the elementary forces are said to be parallel which concludes the fact that (Resultant force=Total pressure) but if it is curved then the elementary forces are not parallel and there will be components opposing each other then the Resultant pressure will be less than the Total Pressure. Total pressure and Resultant pressure is a force not the intensity of pressure. The surfaces in which the hydrostatic force acts can be either PARTLY SUBMERGED or FULLY SUMERGED.PARTLY SUBMERGED means the surface is partly covered by a fluid then FULLY SUBMERGED means the surface is fully covered by water. PARTLY SUMERGED is illustrated as follows. Then FULLY SUBMERGED is illustrated as follows.
For partly submerged surfaces we use the following equations to calculate the unknowns.(yd)
Resultant force=R=1/2 pgby ̅(theoretical) y ̅=y-d/2
Centre of Pressure=D=((by^3)/12)/(bdy ̅ )+y ̅ D-y ̅=d^2/(12y ̅ )
Moment of R_exp=R_exp (a+d/2+d^2/(12y ̅ )) (experimental)
Moment of R_exp=Moment of weight=mgl
R_exp (a+d/2+d^2/(12y ̅