Fluid Mechanics

21. A piece of wood having weight 5 kg floats in water with 60% of its volume under the liquid. The specific gravity of wood is

  1. 0.83
  2. 0.6
  3. 0.4
  4. 0.3
  5. none of the above.

Correct answer: (B)
0.6

22. A piece weighing 3 kg in air was found to weigh 2.5 kg when submerged in water. Its specific gravity is

  1. 1
  2. 5
  3. 7
  4. 6
  5. 8

Correct answer: (D)
6

23. A pressure of 25 m of head of water is equal to

  1. 25 kN/m2
  2. 245 kN/m2
  3. 2500 kN/m2
  4. 2.5kN/m2
  5. 12.5 kN/m2.

Correct answer: (B)
245 kN/m2

24. A ship whose hull length is 100 m is to travel at 10 m/sec. For dynamic similarity, at what velocity should a 1:25 model be towed through water ?

  1. 10 m/sec
  2. 25 m/sec
  3. 2 m/sec
  4. 50 m/sec
  5. 250 m/sec.

Correct answer: (C)
2 m/sec

25. A square surface 3 m x 3 m lies in a vertical line in water pipe its upper edge at water surface. The hydrostatic force on square surface is

  1. 9,000 kg
  2. 13,500 kg
  3. 18,000 kg
  4. 27,000 kg
  5. 30,000 kg.

Correct answer: (B)
13,500 kg

26. A streamline is defined as the line

  1. parallel to central axis flow
  2. parallel to outer surface of pipe
  3. of equal yelocity in a flow
  4. along which the pressure drop is uniform
  5. which occurs in all flows.

Correct answer: (C)
of equal yelocity in a flow

27. According to Bernoulli's equation for steady ideal fluid flow

  1. principle of conservation of mass holds
  2. velocity and pressure are inversely proportional
  3. total energy is constant throughout
  4. the energy is constant along a stream-line but may vary across streamlines
  5. none of the above.

Correct answer: (D)
the energy is constant along a stream-line but may vary across streamlines

28. According to the principle of buoyancy a body totally or partially immersed in a fluid will be lifted up by a force equal to

  1. the weight of the body
  2. more than the weight of the body
  3. less than the weight of the body
  4. weight of the fluid displaced by the body
  5. weight of body plus the weight of the fluid displaced hy the body.

Correct answer: (D)
weight of the fluid displaced by the body

29. Alcohol is used in manometers because

  1. it has low vapour pressure
  2. it is clearly visible
  3. it has low surface tension
  4. it can provide longer column due to low density
  5. is provides suitable meniscus.

Correct answer: (D)
it can provide longer column due to low density

30. All the terms of energy in Bernoulli's equation have dimension of

  1. energy
  2. work
  3. mass
  4. length
  5. time.

Correct answer: (D)
length

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