Question

Question 3 (a) (i) A sealed lightweight plastic cube of sides 0.75m is submerged under water, as shown in Figure Q3a. Find the net hydrostatic forces acting on the cube. [8] (ii) If the cube is lowered further in the water, what effect does this have on the hydrostatic forces? (iii) If the cube must be maintained in the location shown in Figure Q3a using a rope tied to a concrete block, what volume of concrete is required? [1] (Note: acceleration due to gravity g=9.81 m²/s; water density p= 1000 kg/mº; concrete density p = 2400 kg/m) Water surface Figure Q3a

Answer 1

10.754 MOCNont of cube or to hold. It in Solus. Hyd05.dalie Porec. arting on cube - R let cube is xn from the surface of water Ixn. Net ta tie force coill be = Yu (0.15+X54A2 -rw xx xA2 fw =-|(1810(0.75+6)x0.753) – (981920 x 38.159) fw 981000.752 (0.75+*--* *) fwa 9810%(0.7593 4188.59 N. i gf cube is loucesied. Swerthes then also hydrostatic domes while not change case use can see from aboul Solutioki ule haue calculated cpusaid. Poree cube acting So conceete block will have to 41138.59 n force to Position (ii) on is 4138.59 n. prenent upuland.

(M) concrete o volume of concrete net hydrostatic force on cute. (240009.81) x volume of concute = 4138.59 volume of concrete (240049.81) volume of concrete = 4138.59 = 0.17513