### FLUID MECHANICS (OBJECTIVE)

#### Some important question from fluid mechanics

1- The total pressure on a horizontally immersed surface is (where w = Specific weight of the liquid, A = Area of the immersed surface, and x = Depth of the centre of gravity of the immersed surface from the liquid surface)
(A) wA             (B) wx
(C) wAx           (D) wA/x
(Ans: C)
2- Streamline and equipotential lines in a flow field
(A) are parallel to each other
(B) are identical to each other
(C) are perpendicular to each other
(D) intersect at acute angles
(Ans: C)
3- The discharge of a depressed nappe is 6 to 7 percent __________ that of a free nappe.
(A) Less than
(B) More than
(C) Equal to
(D) None of these
(Ans: B)
4-When a body is placed over a liquid, it will sink down if
(A) Gravitational force is equal to the up-thrust of the liquid
(B) Gravitational force is less than the up-thrust of the liquid
(C) Gravitational force is more than the up-thrust of the liquid
(D) None of the above
(Ans: C)
5-The property by virtue of which a liquid opposes relative motion between its different layers is called
(A) Surface tension
(B) Coefficient of viscosity
(C) Viscosity
(D) Osmosis
(Ans: C)
6-A weir is said to be narrow-crested weir, if the width of the crest of the weir is __________ half the height of water above the weir crest.
(A) Equal to
(B) Less than
(C) More than
(D) None of these
(Ans- B)
7- Euler's dimensionless number relates the following
(A) Inertial force and gravity
(B) Viscous force and inertial force
(C) Viscous force and buoyancy force (D) Pressure force and inertial force
(Ans- D)
8 When a body floating in a liquid, is displaced slightly, it oscillates about
(A) C.G. of body
(B) Center of pressure
(C) Center of buoyancy
(D) Metacentre
(Ans: D)
9- A Newtonian fluid is defined as the fluid which
(A) Obeys Hook’s law
(B) Is compressible
(C) Obeys Newton’s law of viscosity
(D) Is incompressible
(Ans: C)
10- If the Reynolds number is less than 2000, the flow in a pipe is
(A) Turbulent
(B) Laminar
(C) Transition
(D) None of the above
(Ans: B)
11- A flow is called super-sonic if the
(A) Velocity of flow is very high
(B) Discharge is difficult to measure
(C) Mach number is between 1 and 5
(D) Mach number is less than 1
(Ans: C)
12-The unit of pressure one bar is
(A) 1 Pascal
(B) 1 kilo Pascal
(C) 100 k Pascal
(D) 1000 k Pascal
(Ans: C)
13- A flow is called super-sonic if the
(A) Velocity of flow is very high
(B) Discharge is difficult to measure (C) Mach number is between 1 and 6 (D) None of these
(Ans: C)
14- The dynamic viscosity of a liquid is 1.2 × 10-4 Ns/m2, whereas, the density is 600 kg/m3. The kinematic viscosity in m2/s is
(A) 72 × 10-3
(B) 20 × 10-8
(C) 7.2 × 103
(D) 70 × 106
(Ans: B)
15- The location of the centre of pressure over a surface immersed in a liquid is
(A) Always above the centroid
(B) Will be at the centroid
(C) Will be below the centroid
(D) For higher densities it will be above the centroid and for lower densities it will be below the centroid
(Ans: C)
16- The continuity equation is the result of application of the following law to the flow field
(A) First law of thermodynamics
(B) Conservation of energy
(C) Newtons second law of motion
(D) Conservation of mass
(Ans: D)
17- The pressure of the liquid flowing through the divergent portion of a Venturimeter
(A) Remains constant
(B) Increases
(C) Decreases
(D) Depends upon mass of liquid
(Ans: C)
18- When the Mach number is between __________ the flow is called super-sonic flow.
(A) 1 and 2.5
(B) 2.5 and 4
(C) 4 and 6
(D) 1 and 6
(Ans: D)
19- In an immersed body, centre of pressure is
(A) At the centre of gravity
(B) Above the centre of gravity
(C) Below be centre of gravity
(D) Could be above or below e.g. depending on density of body and liquid
(Ans: C)
20- Steady flow occurs when
(A) The direction and magnitude of the velocity at all points are identical (B) The velocity of successive fluid particles, at any point, is the same at successive periods of time
(C) The magnitude and direction of the velocity do not change from point to point in the fluid
(D) The fluid particles move in plane or parallel planes and the streamline patterns are identical in each plane (Ans: B)
21- In a forced vortex, the velocity of flow everywhere within the fluid is
(A) Maximum
(B) Minimum
(C) Zero
(D) Nonzero finite
(Ans: D)
22- Bernoulli’s equation cannot be applied when the flow is
(A) Rotational
(B) Turbulent
(D) All of the above
(Ans: D)
23- The line of action of the buoyant force acts through the Centroid of the (A) Submerged body
(B) Volume of the floating body
(C) Volume of the fluid vertically above the body
(D) Displaced volume of the fluid
(Ans: D)
24- During the opening of a valve in a pipe line, the flow is