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Assertion (A): If a cube is placed in a liquid with two of its surfaces parallel to the free surface of the liquid, then the pressures on the two surfaces which are parallel to the freesurface, are the same.
Reason (R): Pascal's law states that when a fluid is at rest, the pressure at any plane is the same in all directions.
The reading of the pressure gauge fitted on a vessel is 25 bar.The atmospheric pressure is 1.03 bar and the value of g is9.81m/s2. The absolute pressure in the vessel is:
Ans. (c) Absolute pressure = Atmospheric pressure + Gauge Pressure = 25+1.03 = 26.03 bar
Which one of the following pairs is not correctly matched?
Ans. (d) External diffuser is creating centrifugal head.
For pumping molasses, it is preferable to employ
Air vessel is used in a reciprocating pump to obtain
If a reciprocating pump having a mechanical efficiency of 80% delivers water at the rate of 80 kg/s with a head of 30 m, the brake power of thepump is:
Match List-I (Type of pumps) with List-II (Associated features) and select the correct answer using the codes given below the Lists:
Whenever a plate is submerged at an angle with the direction of flow ofliquid, it is subjected to some pressure. What is the component of thispressure in the direction of flow of liquid, known as?
The drag force exerted by a fluid on a body immersed in the fluid is dueto:
Which one of the following causes lift on an immersed body in a fluidstream?
Match List-I with List-II and select the correct answer:
Ans. (c) In non-dimensional form, the vortex shedding frequency is expressed as as
the Strouhal number named after V. Strouhal, a German physicist who experimented with wires singing in the wind. The Strouhal number shows a slight but continuous variation with Reynolds number around a value of 0.21.
Direction of flow, drag force is essentially a function of the Reynoldsnumber of the flow.
Reason (R): As Reynolds Number is about 100 and above, eddies formedbreak away from either side in periodic fashion, forming a meanderingstreet called the Karman Vortex street.
Ans. (a) Both A and R are true and R provides a correct explanation of A.
When pressure drag over a body is large as compared to the friction drag, then the shape of the body is that of:
The critical value of Mach number for a subsonic airfoil is associatedwith sharp increase in drag due to local shock formation and itsinteraction with the boundary layer. A typical value of this criticalMach number is of the order of:
Ans. (c) The critical Mach number is defined as free stream Mach number at which Sonic flow (M = 1) is first achieved on the airfoil surface. Critical value of mach number for a subsonic airfoil is 1.1 to 1.3.
Assertion (A): A body with large curvature causes a larger pressure drag and, therefore, larger resistance to motion.
Reason (R): Large curvature diverges the stream lines, decreases the velocity resulting in the increase in pressure and development of adverse pressure gradient leading to reverse flow near the boundary.
Consider the following coefficients: (Re = Reynolds number)
1. 1.328 Re_ (0.5) for laminar flow
2. 2.072 Re_ (0.2) for turbulent flow
3. 0.072 Re _ (0.2) for turbulent flow
4. 1.028 Re _ (0.5) for laminar flow
The coefficient of drag for a flat would include
The Magnus effect is defined as
An automobile moving at a velocity of 40 km/hr is experiencing a wind resistance of 2 kN. If the automobile is moving at a velocity of 50 km/hr,the power required to overcome the wind resistance is:
Ans. (a) Power,
= 43.4 kw
Improved streaming produces 25% reduction in the drag coefficient of a torpedo. When it is travelling fully submerged and assuming the driving power to remain the same, the crease in speed will be:
A parachutist has a mass of 90 kg and a projected frontal area of 0.30m2 in free fall. The drag coefficient based on frontal area is found to be 0.75. If the air density is 1.28 kg/m3, the terminal velocity of the parachutist will be:
Total Drag (FD) = Weight (W)