An isosceles triangular plates of base 3 m and altitude 3 m is immersed in oil vertically with its base coinciding with the free surface of the oil of relative density 0.8. Determine the total thrust.

Area of the plate =1/2× base × altitude =1/2×3×3=4.5m2 Density of oil =0.8×1000=800kgm−3  Depth of c.g. of the plate from the free surface =h3=(1/3)3=1mPressure at COM of plate=ρgh3=800×10×1 PaNet thrust force acts at center of mass of plate. Now, total thrust on the plate =  (plate area) × (pressure at the c.g. of the plate) =(4.5)(800×10×1)=36kN