Question

A rectangular plane surface 2m wide and 3m deep lies in water in such a way that its plane makes an angle of 30◦ with the free surface of water. Determine the total pressure and position of center of pressure when the upper edge is 1.5m below the free water surface
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Answer 1

Volume of each cube = 64 cm3

∴ Total volume of the two cubes = 2 × 64 cm3

= 128 cm3

Let the edge of each cube = x

∴ x3 = 64 = 43

∴ x = 4 cm

Now, Length of the resulting cuboid l = 2x cm

Breadth of the resulting cuboid b = x cm

Height of the resulting cuboid h = x cm

∴ Surface area of the cuboid = 2 (lb + bh + hl) = 2[(2x . x) + (x . x) + (x . 2x)]

= 2[(2 × 4 × 4) + (4 × 4) + (4 × 2 × 4)] cm2

= 2 [32 + 16 + 32] cm2 = 2[80] cm2 = 160 cm2.