Fluid Mechanics (Part-2) (General Engineering) (SSC JE)

Total Questions: 50

31. Density of water is maximum at - [RSMSSB JE (E&M) Degree - 26/12/2020 ]

Correct Answer: (c) 4⁰C
Solution:

Density of water is maximum at 4ºC becasue volume of water decreases from 0ºC to 4ºC and minimum at 4ºC.
Density, ρ = (m/v)

32. Which of the following has no unit ? [RSMSSB JE (E&M) Degree - 26/12/2020 ]

Correct Answer: (d) Strain
Solution:

Strain–It is defined as the ratio of change in length to its original length. It is unit less because of relation between same type of physical quantity.

33. The depth of centre of pressure for an immersed surface inclined at an angle θ with the liquid surface lies at a distance equal _____ the centre of gravity. [RSMSSB JE (E&M) Degree - 26/12/2020 ]

Correct Answer: (a)
Solution:

Centre of pressure of an inclined surface

34. According to equation of continuity - [RSMSSB JE (E&M) Degree - 26/12/2020 ]

Correct Answer: (c) a₁ v₁ = a₂ v₂
Solution:

Equation of continuity–It is based on the principle of "conservation of mass".

35. If F is the Froude number for a flow in a triangular channel, then the Froude number for same velocity and same depth of flow in a rectangular channel will be [RSMSSB JE (E&M) Degree - 26/12/2020 ]

Correct Answer: (b) √2F
Solution:

36. According to classification based on operating head on turbines, the head of medium head plant is [BPSC AE (Civil) 25.03.2022 ]

Correct Answer: (d) None of the above
Solution:

Classification of turbines based on operating head.
1. High head turbine : (500 – 2000) m
Example–Pelton wheel etc.
2. Medium head turbine : (30 – 500) m
Example–Francis etc.
3. Low head turbine : < 30 m
Example–Kaplan etc.
Note : The commission has accepted option (b) is correct.

37. Which turbine gives the highest efficiency? [RSMSSB JE (E&M) Degree - 26/12/2020 ]

Correct Answer: (a) Kaplan
Solution:

Kaplan is inward flow reaction turbine which has highest efficiency at very low operating head (upto 30 m).

38. The discharge Q in a triangular weir varies as [BPSC AE (Civil) 25.03.2022 ]

Correct Answer: (d)
Solution:

39. In a super-critical flow in a rectangular channel, a smooth expansion changes the width from B₁ to B₂. This causes the water surface elevation after the expansion to

Correct Answer: (b) decrease
Solution:


1. In super critical flow due to expansion of open channel flow depth decreases.
2. In sub critical flow due to expansion of open channel flow depth increase.
• When the depth of flow in a channel is greater than critical depth the flow is said to be sub-critical flow. Froude number is less than 1 for sub-critical flow.
• When the depth of flow in a channel is less than critical depth the flow is said to be super-critical flow. Froude number is greater than 1 for supercritical flow.

40. The term 'alternate depths' is used in openchannel flow to denote the depths [BPSC AE (Civil) 25.03.2022 ]

Correct Answer: (c) having the same specific energy for a given discharge
Solution:


• Alternate depth is used in open channel flow to denote the paired flow depth having the same specific energy for a given discharge.
Critical depth–The depth of flow at which the discharge is maximum for a given specific energy or the depth at which a given discharge occurs with minimum specific energy.
Sequent/conjugate depths–The two possible depths (y₁, y₂) that have the same specific force are known as sequent depths.
Normal depth–When the slope of the water surface and channel bottom is the same and the water depth remains constant is known as normal depth.