Aerodynamics Multiple Choice Questions & Answers (MCQs) on “Bernoulli’s Equation”.
1. The relation between pressure and velocity in an inviscid, incompressible flow is given by __________
a) p = constant
b) p + 0.5ρ*V2 = constant
c) 0.5ρ*V2 = 0
d) p + 0.5ρ*V2 = 0
Answer: b
Clarification: The relation between pressure and velocity can be given by p+0.5ρ*V2 = constant which is called as Bernoulli’s equation. In the above equation, p is the pressure and V is the velocity which implies that as the pressure increases, velocity decreases and vice versa.
2. The aircraft fly based on which principle _________
a) Newton’s third law
b) Conservation of mass
c) Bernoulli’s principle
d) Gravity
Answer: c
Clarification: An aircraft fly based on Bernoulli’s principle. As the air speed increases, the pressure decreases which results in high lift generation. According to this principle, the pressure is inversely proportional to velocity.
3. Bernoulli’s equation is applicable only for _______
a) Irrotational flow
b) Viscous flow
c) Inviscid, incompressible flow
d) Compressible flow
Answer: c
Clarification: Bernoulli’s equation is applicable only for inviscid and incompressible flow because in inviscid flow, the viscosity is zero and hence no viscous forces acts on the body also incompressible flow means the density remains constant. The inviscid and incompressible flow reduces many fluid problems.
4. The point where the fluid comes to rest is called as ___________
a) Rest point
b) Stagnation point
c) Viscous point
d) Boundary layer point
Answer: b
Clarification: Stagnation point is the point where the flow slows down and come to rest. The streamline divides the flow into two parts- the upper flow and the lower flow. At a point, the flow cannot enter into an object so it has to stop and that point is called a stagnation point.
5. Stagnation pressure or the total pressure is the sum of _________
a) Kinetic and potential energy
b) Static and dynamic pressure
c) Kinetic energy +potential energy +gravity
d) Cannot be determined
Answer: b
Clarification: The total pressure or stagnation pressure is the sum of static and dynamic pressure. Let p0 be the total pressure, ps be the static pressure and pd be the dynamic pressure.
Therefore, p0 = ps + pd.
6. The dynamic pressure is given by ______
a) 0.5ρ*V2
b) ρ* V2
c) 3*V2
d) 5ρ* V2
Answer: a
Clarification: The dynamic pressure is not actually a pressure. It simply justifies the decrease in pressure due to the increase in the velocity. It simply justifies that when the density is half and the velocity is squared, the pressure decreases.
7. The coefficient of pressure at stagnation point is ___________
a) 0
b) 0.5
c) 1
d) 2
Answer: c
Clarification: The coefficient of pressure is the dimensional less quantity and it describes the relative pressure at each and every point in a flow field. At stagnation point, its value is maximum and it can change from point to point in a flow field.
8. The pressure for an ideal gas can be given by ____________
a) pV=nRT
b) p=RT
c) pV=T
d) p=VT
Answer: a
Clarification: In an ideal gas, molecules does not have volume and hence they do not interact with each other. For an ideal gas, the pressure is directly proportional to temperature and is inversely proportional to volume.
9. Bernoulli’s equation can be directly applied to viscous flow.
a) True
b) False
Answer: b
Clarification: No, the Bernoulli’s equation cannot be directly applied to viscous flow because in viscous flow, the motion of the fluid particle is constant. Hence, we need to convert the viscous flow into Navier-stoke equation and then Bernoulli’s equation can be applied to it.
10. Bernoulli’s equation can be applied to compressible flow at which of the following matches the number?
a) mach number less than 1
b) mach number equal to 1
c) higher mach numbers
d) does not depends on mach number
Answer: c
Clarification: Bernoulli’s principle states that increasing the velocity decreases the pressure which gives us a higher lift. If the matches the number increases, gradually the pressure decreases which leads to an increase in lift.
11. Bernoulli’s principle is derived from which of the following?
a) Conservation of mass
b) Conservation of energy
c) Newton’s law of motion
d) Conservation of momentum
Answer: b
Clarification: It states that the sum of all the forms of energy in flow is the same at all the points in that flow field. The energy here refers to kinetic energy, potential energy and internal energy.
12. An increase in the speed of the flow leads to an increase in kinetic energy and dynamic pressure.
a) True
b) False
Answer: a
Clarification: An increase in speed of the flow leads to an increase in kinetic energy and dynamic pressure (0.5ρ*V2). As the dynamic pressure increases that is the density is halved and the velocity is squared, the static pressure decreases along with the decrease in potential energy and internal energy.