# Fluid Mechanics Questions and Answers – Force Exerted by a Jet on a Series of Vanes

This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Force Exerted by a Jet on a Series of Vanes”.

1. Principle of fluid mechanics works on the utilization of________
a) Accelerating mass
b) Volume
c) Work
d) Velocity

Explanation: The Principle of fluid mechanics works on the utilization of useful work. The working is based on the force exerted by a fluid jet striking the surface and moving over a series of vanes about its axis.

2. The propulsive force drives the jet in the ________
a) Backward direction
b) Forward direction
c) Perpendicular direction
d) Parallel movement

Explanation: Force exerted by a jet on a moving plate happens in three cases. The three cases are classified depending on their position. The propulsive force drives the jet in the forward direction. A good example is the aircraft or a boat.

3. The force analysis on a curved vane is understood using______
a) Velocity triangles
b) Angle of the plate
c) Vane angles
d) Plate dimensions

Explanation: The force analysis on a curved vane is understood using clearly using the study of velocity triangles. There are two types of velocity triangles, inlet velocity triangle and outlet velocity triangle.

4. Jet propulsion works on the principle of________
a) Newton’s first law
b) Newton’s second law
c) Newton’s third law
d) Thermodynamic properties

Explanation: Jet propulsion works on the principle of Newton’s third law. Newton’s third law states that for every action, there is an equal and opposite reaction. Thus, the correct option is Newton’s third law.

5. How is absolute velocity at inlet denoted?
a) V
b) V1
c) C
d) v

Explanation: In a jet propulsion, V1 stands for absolute velocity at the inlet. The main application in which this equation is applied is for a jet propulsion in the tank with orifice. Thus, the correct option is ‘b’.
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6. The relative velocity is obtained by the equation_________
a) u – V1
b) V1
c) u*V1
d) u/V1

Explanation: The relative velocity of the jet is denoted as Vr1. It is the relative velocity at the inlet to the vane. Relative velocity of inlet to the vane is obtained by subtracting vectorially the velocity of the vane with its absolute velocity.

7. If the friction is neglected, then_______
a) Vr1 > Vr2
b) Vr1 < Vr2
c) Vr1 = Vr2
d) Vr1 is a zero

Explanation: The relative velocity of the jet is denoted as Vr1. It is the relative velocity at the inlet to the vane. Relative velocity of inlet to the vane is obtained by subtracting vectorially the velocity of the vane with its absolute velocity. It happens in the same way for Vr2. Thus, If the friction is neglected, then Vr1 = Vr2.

8. If the pressure remains a constant, then ________
a) Vr1 > Vr2
b) Vr1 < Vr2
c) Vr1 = Vr2
d) Vr1 is a zero

Explanation: The relative velocity of the jet is denoted as Vr1. It is the relative velocity at the inlet to the vane. Relative velocity of inlet to the vane is obtained by subtracting vectorially the velocity of the vane with its absolute velocity. It happens in the same way for Vr2. Thus, If the pressure remains a constant, then Vr1 = Vr2.

9. Through inlet orifices, which are facing the direction of motion of the ship, the water from the sea can be taken by the pump.
a) True
b) False

Explanation: Through inlet orifices, which are facing the direction of motion of the ship, the water from the sea can be taken by the pump. We can also take the sea water from the pump when the inlet orifices are at right angles with respect to the motion of the ship.

10. The efficiency of the vane is given by_________
a) 1-V22/ V12
b) 1-(V22/ V12)
c) V22/ V12
d) 1- V12

Explanation: In a velocity triangle at the inlet and the outlet, the control volume is moving with a uniform velocity. Therefore, the momentum theorem of the control volume is at a steady flow. Thus, the efficiency of the vane is given by 1-(V22/ V12).

11. A jet strikes a curved plate at its ______
a) Sides
b) Surface
c) Centre
d) Does not strike

Explanation: A jet strikes a curved plate at its centre. Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. The three cases are when plate is vertical, plate is inclined and plate is curved with respect to the jet.

12. Jet propulsion of ship is less efficient than screw propeller due to_______
a) Pressure
b) Temperature
c) Frictional losses
d) Wear and tear

Explanation: Jet propulsion of ship is less efficient than screw propeller due to large amount of frictional losses developed in the pump and the pipeline. Thus, it is rarely used in ships.

13. Jet propulsion of ship in a very shallow water is needed to_________
a) Avoid sinking of the ship
b) Avoid damage of the propeller
c) Avoid current directions
d) Avoid surface damage

Explanation: Jet propulsion of ship in a very shallow water is needed to avoid damage of the propeller. Jet propulsion of ship is less efficient than screw propeller due to large amount of frictional losses developed in the pump and the pipeline.

14. A turbojet does not consist of which of the following component?
a) Compressor
b) Combustion chamber
c) Gas turbine
d) Air filter

Explanation: A turbojet consists of four major components for an efficient working. The four components are compressor, combustion chamber, gas turbine and a nozzle. Air filter is not used in a turbojet.

15. Which among the following is not a type of jet engine?
a) Turbojet
b) Ramjet
c) Scramjet
d) Propulsive jet

Explanation: A jet engine is broadly classified into four types of jet. The four types of jet are turbojet, ramjet, scramjet, and pulse jet. There isn’t anything related to the propulsive jet and thus cannot be the answer.

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