Buoyancy and Floatation MCQ – Fluid Mechanics

51. A metal body floats at the interface of water and oil (sp. gr. = 0.85) such that 35% of its volume is submerged in water and 65% in oil. The density of metal would be

  1. 852.5 kg/m3
  2. 912.5 kg/m3
  3. 902.5 kg/m3
  4. cannot be determined
Answer
Answer. c

52. When a ship enters sea from river, one can expect it to

  1. rise a little
  2. sink a little
  3. remain at the same level of the draft
  4. rise or fall depending on whether it is of steel or Wood
  5. sink if temperature difference between the river and seawater is more than 2 °C
Answer
Answer. a

53. A uniform body 3 m long, 2 m wide and 1 m deep floats in water. f the depth of immersion is 0.6 m then the weight of the body is

  1. 3.53 kN
  2. 33.3 kN
  3. 35.3 kN
  4. 45.6 kN
Answer
Answer. c

54. Calculate the volume of the water displaced and position of centre of buoyancy, respectively, for a wooden block of width 2.5 m and of depth 1.5 m, when it floats horizontally in water. The density of wooden block is 650 kg/m3 and its length 6 m.

  1. 14.62 m3 and 0.487 m from base
  2. 16.67 m3 and 0.762 m from base
  3. 16.67 m3 and 0.487 m from base
  4. 14.62 m3 and 0.762 m from base
Answer
Answer. a

55. A solid cylinder of diameter 3 m has a height of 2 m. What would be the metacentric height of cylinder when it is floating in water with its axis vertical? The specific gravity of cylinder is 0.7.

  1. 0.30 m
  2. 0.1017 m
  3. 1.4 m
  4. 0.4017 m
Answer
Answer. b

56. A block of wood 2 m long, 2 m wide and 1 m deep is floating horizontally in water. If density of wood is 800 kg/m3, then the volume of water displaced will be

  1. 3.2 m3
  2. 2.6 m3
  3. 2 m3
  4. 6 m3
Answer
Answer. a

57. A stone weight 450 N in air and 250 N in water. The volume of the stone is

  1. 0.0204 m3
  2. 0.204 m3
  3. 1.0204 m3
  4. 1.0402 m3
Answer
Answer. a

58. A 15 cm length of steel rod with relative density of 7.5 is submerged in a two layer fluid. The bottom layer is mercury and the top layer is water. The height of top surface of the rod above the liquid interface (in cm) is

  1. 7.38
  2. 7.64
  3. 7.82
  4. 8.24
Answer
Answer. a

59. An open vertical rectangular tank is provided with a circular hole of 3 m diameter on one of its vertical sides. This hole is closed by a disk of 3 m diameter that can rotate about the horizontal diameter. When the water level in the tank is 4 m above the centre of the disk, the torque required to maintain the disk in equilibrium will be nearly

  1. 39 kNm
  2. 33 kNm
  3. 28 kNm
  4. 23 kNm
Answer
Answer. a
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