# Fluid Mechanics Questions and Answers – Introduction, Euler’s and Bernoulli’s Equation of Motion

This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Introduction, Euler’s and Bernoulli’s Equation of Motion”.

1. Which forces are neglected to obtain Euler’s equation of motion from Newton’s second law of motion?
a) Viscous force, Turbulence force, Compressible force
b) Gravity force, Turbulence force, Compressible force
c) Body force, Gravity force, Turbulence force
d) Viscous force, Turbulence force, Body force

Explanation: Viscous force, Turbulence force, Compressible forces are neglected to obtain Euler’s equation of motion from Newton’s second law of motion.

2. Navier-Stoke’s equation can be obtained from Reynolds’s equation by not considering which type of force?
a) Turbulence force
b) Gravity force
c) Compressible force
d) Viscous force

Explanation: Navier-Stoke’s equation can be obtained from Reynolds’s equation by not considering Turbulence force.

3. In order to apply Bernoulli’s equation across two sections, we have to obtain it from Euler’s equation. What is the operation that needs to be carried out in order to obtain it from Euler’s equation?
a) Partial Differentiation
b) Differentiation
c) Integration
d) None of the mentioned

Explanation: We have to integrate the Euler’s equation to obtain Bernoulli’s equation from it.

4. Which of the following assumption is incorrect in the derivation of Bernoulli’s equation?
a) The fluid is ideal
c) The flow is incompressible
d) The flow is rotational

Explanation: The assumption made is that the flow is irrotational.

5. From mathematical perspective if for a fluid curl of velocity vector is some constant value, it is ideal, steady and incompressible, then we can apply Bernoulli’s equation.
a) True
b) False

Explanation: If curl is some constant value, the fluid is irrotational and hence, Bernoui can’t be applied.
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6. If in a fluid, while applying Newton’s second law of motion, compressibility force is neglected then what equation is obtained?
a) Navier Stoke’s Equation
b) Reynold’s equation of motion
c) Euler’s Equation of motion
d) Continuity Equation for fluid flow

Explanation: If in a fluid, while applying Newton’s second law of motion, compressibility force is neglected then Reynold’s equation of motion is obtained.

7. According to statement of Bernoulli’s theorem if Kinetic or Potential Energy is changing then overall energy changes and hence energy is not constant at all the places.
a) True
b) False

Explanation: Energy remains constant at all point as per statement of Bernoulli’s theorem even if Kinetic or Potential Energy is changing.

8. In derivation for Euler’s equation, the weight of fluid element is considered as negligible and ignored in calculation.
a) True
b) False

Explanation: The weight of fluid element even though negligible is consideration in calculation.

9. Water is flowing through a pipe of 3.8 cm diameter under a pressure of 20 N/cm2 (gauge) and with mean velocity of 3.7 m/s. Find the total head or total energy per unit weight of the water at a cross section, which is 7 m above the datum line.
a) 56.14 m
b) 28.07 m
c) 84.18 m
d) 10.52 m

= p/ρg + v2/ 2g + z
= 20.38 + 0.69 + 7
= 28.07 m.

10. A fluid with specific gravity 0.85 is flowing through a diameter 250 mm and 150 mm at the bottom and upper ends respectively. Determine the difference in datum head if the rate of flow through pipe is 0.04 m3/s. Take pressure at top and bottom as 27 N/cm2 and 10 N/cm2.
a) 17.1 m
b) 34.2 m
c) 10.5 m
d) None of the mentioned

Hence, Datum head difference = 17.1 m.

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