• unanswered questions or grayed questions are not specifically tested on the exams but may still be of interest
  • Answers in bold have been discussed in class
  • The topics related to answers in italics have been discussed in class, but the concept question itself has not and probably won’t be unless one of you brings it up
  • questions in lavender are less likely to be important for the multiple-choice portion of the exams

Links below break these questions up by exam (e.g., you need only study up to the exam 1 link for exam 1)

exam1

exam2

exam3

ConcepTest Question

“fluids magnitudes 1”

Later we will learn about buoyancy, a concept that may already be familiar to you. A consequence: when you weigh yourself on a scale, you underestimate your true weight by the weight of the air you displace.
Typically, what is this error (how many pounds does a volume of ordinary air the size of an average person weigh)?

a)1.5 pounds

b)0.15 pounds

c)0.015 pounds

d)0.0015 pounds

ConcepTest Question

“fluids magnitudes 2”

Water is approximately how many times more dense than air?

a)30

b)100

c)300

d)1000

e)3000

ConcepTest Question

“fluids magnitudes 3”

Comparing any gas to its liquid version (e.g., steam to liquid water, nitrogen to liquid nitrogen, etc.), the gas is 300-3000 times less dense than the liquid.

a)true

b)false

ConcepTest Question

“fluids magnitudes 4”

A typical barometric pressure is 14.7 psia. What would the barometric pressure have to rise to for the windows (simple plates of glass) on a typical building to shatter?

a)14.8 psia

b)15.7 psia

c)147 psia

d)much higher than 147 psia

ConcepTest Question

“what is psia”

What is the difference between psi, psig, psia?

a)There is no difference

b)Psia is relative to a perfect vacuum, whereas psig is relative to something else (typically the barometric pressure) and psi is ambiguous

c)Psia stands for “pounds per square inch of area”

ConcepTest Question

“fluids magnitudes 5”

Imagine a building sitting in a world at 14.7 psia. What would the pressure increase in the building, relative to the outside world, have to be to cause the windows to shatter?

a)0.1 psig

b)1 psig

c)10 psig

d)100 psig

ConcepTest Question

“clothes dryer”

If you go outside and feel the exhaust of the dryer in my house the flow feels “weak”. Which of the following are likely to increase the mass flow rate of air leaving the house through the dryer vent:

a) Cleaning the hose connecting the dryer to the outside world.

b)Lengthening the hose.

c) Increasing the inside diameter of the hose.

d)Installing a new hose with a smoother surface finish

ConcepTest Question

“definition of fluid”

A fluid is:

a)A substance in liquid phase.

b)A substance that deforms continuously under the action of a shear stress.

c)A substance that fills the volume of the container in which it is placed.

ConcepTest Question

“what is a shear stress”

Shear stress:

a) has dimensions of force/unit area.

b)has units of N.

c) acts in a direction parallel to the pressure.

ConcepTest Question

“no slip”

The no-slip condition:

  1. is an effect that really happens in nature.
  2. is a statement of experimental observation that the velocity of the fluid in contact with a surface is equal to the velocity of that surface.
  3. was determined from fundamental principles of Newtonian mechanics.
  4. depends on the roughness of the surface.

ConcepTest Question

“figure 1.1 question 1”

Given the following diagram for the definition of a fluid:

This figure is a depiction of the behavior of a fluid under the action of a constant shear force.

Given this, what is the difference in the velocity of any fluid element between t1 and t2?

  1. There is no difference
  2. The velocity at t1 is greater than the velocity at t2
  3. The velocity at t2 is greater than the velocity at t1.

ConcepTest Question

“figure 1.1 question 2”

Given the following diagram for the definition of a fluid:

This figure is a depiction of the behavior of a fluid under the action of a constant shear force.

Given this, what is the difference in the velocity gradient of the fluid between t1 and t2?

  1. There is no difference
  2. The velocity gradient at t1 is greater than the velocity gradient at t2
  3. The velocity gradient at t2 is greater than the velocity gradient at t1.

ConcepTest Question

“figure 1.1 question 3”

Given the following diagram for the definition of a fluid:

This figure is a depiction of the behavior of a fluid under the action of a constant shear force.

Given this, if the viscosity of the fluid is somehow made to be infinite and the fluid slip at the top plate is somehow made to be infinite, which of the following are true?

  1. The magnitude of the horizontal fluid force on the lower plate is zero
  2. All of the fluid has a velocity of zero
  3. The upper plate will continue to accelerate while a force is applied, regardless of how long the force is applied.

ConcepTest Question

“figure 1.1 question 4”

Given the following diagram for the definition of a fluid:

This figure is a depiction of the behavior of a fluid element under the action of a constant shear force.

Given this, if the viscosity of the fluid is somehow made to be zero, which of the following are true?

  1. The magnitude of the fluid force on the lower plate is zero
  2. All of the fluid has a velocity of zero
  3. The upper plate will continue to accelerate while a force is applied, regardless of how long the force is applied.

ConcepTest Question

“what’s a basic equation?”

The basic equations governing fluid mechanics:

a) include conservation of mass and Newton’s Law of viscosity

b) include conservation of momentum and the Ideal Gas Equation

c) include conservation of energy and the 2nd law of thermodynamics

ConcepTest Question

“Hooke’s law”

Hooke’s Law, F=-kx, is a description of the force exerted by a spring as a function of the deformation of the spring. Which of the following is true:

  1. Hooke’s Law is considered a fundamental equation, similar to the conservation of mass equation
  2. Hooke’s Law can be used in place of Newton’s 2nd Law if the problem involves a spring
  3. Hooke’s Law was developed from observation of experiments.

ConcepTest Question

“ideal gas equation”

The ideal gas equation is:

  1. a fundamental equation similar to the conservation of mass equation
  2. used to describe the behavior of ideal gases
  3. a model of real gas behavior.

ConcepTest Question

“Brett Favre 1”

Consider Brett Favre playing football. I am interested in knowing how many footballs are on the field of play at any instant in time. Then I am interested in the:

  1. Control Volume Equations applied to the football field
  2. System Equations applied to the football that has just left Brett’s hand
  3. Neither System nor Control Volume Equations
  4. LaGrangian or particle view of the football
  5. Eulerian view of the field

ConcepTest Question

“Brett Favre 2”

Consider the path that a football thrown by Brett Favre follows. Suppose that I am interested in the knowing how far the ball goes. Then I am interested in the:

  1. Control Volume Equations applied to the football field
  2. System Equations applied to the football
  3. Neither System not Control Volume Equations
  4. LaGrangian or particle view of the football
  5. Eulerian view of the field

ConcepTest Question

“differential vs. integral”

Which of the following are true regarding the difference between the integral and differential approach. Again consider the football in flight:

  1. The integral approach is not useful because it does not retain sufficient detail of the flow pattern around the football.
  2. The differential approach allows us to determine flow at any point on the football at any time during the flight of the football.
  3. The combined integral-differential approach is always the best method.

ConcepTest Question

“skydiver 1”

Consider a skydiver in free fall. Which of the basic laws apply to this situation?

  1. The conservation of energy
  2. The second law of thermodynamics
  3. The principle of angular momentum
  4. The conservation of momentum
  5. The conservation of mass

ConcepTest Question

“skydiver 2”

Consider a skydiver in free fall. If we are interested in estimating terminal velocity, which of the basic laws would be useful?

  1. The conservation of energy
  2. The second law of thermodynamics
  3. The principle of angular momentum
  4. The conservation of momentum
  5. The conservation of mass

ConcepTest Question

“skydiver 3”

Consider a skydiver in free fall. If we are interested in estimating terminal velocity, which of the following constitutive equations would be useful?

  1. Hooke’s Law, F=-k*x
  2. Ideal gas law, p=RT
  3. Drag Force, Fdrag = k*V2

ConcepTest Question

“implications of continuum assumption 1”

Because in classical fluid mechanics we treat all fluids using the concept of the continuum:

  1. The effect of individual molecules and atoms in the fluid can be determined.
  2. Each fluid property is assumed to have a definite value at every point in space.
  3. Values of fluid velocity depend on the molecular concentration in that part of the fluid.

ConcepTest Question

“implications of continuum assumption 2”

For a real fluid (which could be different than the ideal continuum we will use in this course):

  1. Below a certain volume of fluid, the density can fluctuate irregularly.
  2. Above a certain volume of fluid, the density can increase or decrease due to large-scale effects.
  3. The density is defined between the two limits associated with a. and b.

ConcepTest Q

“body forces and surface forces”

Examples of a body force and a surface force are:

  1. Gravity is a body force, shear is a surface force.
  2. Gravity is a surface force, pressure force is a body force.
  3. Shear is a body force, pressure is a surface force.

ConcepTest Question

“Newtonian Fluid”

For a Newtonian fluid,

  1. The shear stress is proportional to the velocity gradient in the flow direction
  2. The shear stress is proportional to the absolute viscosity of the fluid
  3. The shear stress is proportional to the velocity gradient perpendicular to the flow direction.

ConcepTest Question

“fluid element at rest”

For a fluid element at rest, the forces acting on the fluid element include:

  1. Gravity forces
  2. Shear forces
  3. Pressure forces

ConcepTest Question

“gradient operator”

The following is true for the gradient operator:

  1. The gradient of a scalar is a vector that points in the direction of maximum rate of increase of the scalar
  2. Ordinarily, the gradient of pressure is zero for a fluid at rest.
  3. Considering the gradient of pressure at the top and bottom of a typical swimming pool, the gradient will be significantly larger near the bottom.

ConcepTest Question

“Hoover dam”

Consider the hydrostatic forces acting a planar submerged surface, such as the surface of a dam. The following is true about the force:

  1. The direction of the force is normal to the surface
  2. The magnitude of the force is equal to the sum total of the pressure force acting on the surface
  3. The pressure on the surface of the dam is a function of elevation

ConcepTest Question

“pressure distributions 1”

Which of the following accurately represents the distribution of absolute pressure on the surface indicated? Assume the pressure is atmospheric outside the container.

(a) (b) (c) (d)ConcepTest Question

“pressure distributions 2”

Which of the following accurately represents the distribution of absolute pressure on the surface indicated? Assume the pressure outside the container is atmospheric.

(a)(b)(c)ConcepTest Question

“pressure distributions 3”

Considering the below representations of absolute pressure distributions on the surface indicated, (d) would be possible if the fluid was ferromagnetic and we could thereby apply a second body force in a new direction of our choice.

(a) true

(b) false
ConcepTest Question “manometers”

Two manometers are shown below. One manometer with a single “U-tube” is connected between tanks “A” and “B”. The other manometer has two U-tubes and is connected between tanks “C” and “D”. The four tanks contain air. The liquid in both manometers is water. Circle the letter of the correct statement.

A (PA – PB) = (PC – PD)/2

B (PA – PB) = 4(PC – PD)

C(PA – PB) = 2(PC – PD)

D(PA – PB) = (PC – PD)/4

E (PA – PB) = (PC – PD)

ConcepTest Question

“integrating pressure”

The pressure force on a submerged surface is defined by the following equation:

When we evaluate the magnitude of the resultant force:

  1. We neglect the minus sign because we know the direction of the force
  2. We include the minus sign to ensure that the sign of the force is correct
  3. We can do either, as long as we know why we are doing it.

ConcepTest Question

“coordinate transformation 1”

Consider the two coordinate axes shown in the figure below:

To transfer from one coordinate system to the other, the following should be used:

  1. x’=x+a
  2. x’=-x+a
  3. x’=-x-a

ConcepTest Question

“coordinate transformation 2”

Consider the diagram above. The absolute pressure at any point in the fluid is given by:

a. P = gh

b.

c.

d.

ConcepTest Question

“uniform vs constant”

Imagine we are viewing the pipe from an Eulerian perspective. For the gas inside the pipe, involved in this steady flow situation, which is/are true?

  1. The density of the gas is uniform
  2. The density is not a function of time
  3. The density is a function of position even though this is a steady flow

ConcepTest Question

“The jellybean jar”

Consider jellybeans being added and removed from a jellybean jar. Only Sam and Sally act on the jar. If the jellybeans are being taken from the jar by Sam at 7 jellybeans per minute and added to the jar by Sally at 5 jellybeans per minute, the rate at which the number of jellybeans in the jar is changing is:

  1. –2 jellybeans
  2. 2 jellybeans
  3. 2 jellybeans/minute
  4. –2 jellybeans/minute
  5. Cannot determine from the information given.

ConcepTest Question

“System form of basic equations”

The following is true of the system form of the basic equations (mass, momentum, angular momentum, energy, and entropy):

  1. The equations apply to a fixed quantity of mass
  2. The equations are formulated in extensive properties
  3. There is a general method to convert the system form to control volume equations
  4. All the basic equations are vector equations.

ConcepTest Question

“identifying extensive properties”

Which of the following are extensive properties?

  1. temperature
  2. internal energy
  3. entropy
  4. specific internal energy
  5. pressure
  6. density
  7. mass

ConcepTest Question

“what’s an extensive property?”

Extensive properties:

  1. Change if the amount of substance we are considering changes
  2. Can be used to determine corresponding intensive properties, i.e., the extensive properties per unit mass
  3. Include pressure and temperature
  4. Can flow in and out of a control volume.

Concept Test Question

“what’s flux”

When a substance is flowing, we often refer to the flux associated with that flow (e.g., mass flux or momentum flux). In this context, when we describe flux, we are referring to:

  1. The transfer rate of an intensive property per unit time
  2. The transfer rate of an extensive property
  3. The transfer of an extensive property per unit area
  4. “Flux capacitors”, as seen in the movie Back to the Future

ConcepTest Question

“reading the conservation of mass equation”

Consider the conservation of mass equation:

In words, this equation reads (select only the single-best answer below):

  1. The mass flow into the control volume is equal to the mass flow out of the control volume
  2. The rate of change of the amount of mass in the control volume is balanced by the net rate at which mass flows out through the control surface
  3. The accumulation of mass in the control volume is balanced by the net rate at which mass flows into the control volume
  4. The fixed amount of mass in the control volume is balanced by the mass that leaves or enters the control volume.

ConcepTest Question

“considering the conservation of mass equation”

The following is/are true for the conservation of mass equation:

  1. It is a scalar equation
  2. There are vectors in the equation
  3. The first term on the right side is zero for steady flow problems if the control volume is fixed
  4. The first term is zero for a single, continuous, incompressible fluid if the control volume is fixed

- exam 1 -

ConcepTest Question

“comparing the mass and momentum basic equations”

When considering the basic equations, the following is/are true:

  1. For conservation of mass and momentum, the rate of change of mass and momentum in the control volume is balanced by the rate at which mass and momentum are flowing out of the control surface.
  2. For conservation of mass, a. is true, but for conservation of momentum, the change in the system momentum can be nonzero.
  3. The system and control volume forms of the conservation of mass equation are the same, however, for the conservation of momentum equation, they are different.

ConcepTest Question

“nozzle 1”

Consider the nozzle on a firehose. The nozzle is connected to the hose via a coupling. When the firehose is in use, the coupling is:

  1. In equilibrium, so there is no force on the coupling.
  2. In tension.
  3. In compression.

ConcepTest Question

“nozzle 2”

Consider the flow exiting from a firehose nozzle when the nozzle is in use. The pressure of the water at the nozzle exit is:

  1. Above atmospheric pressure
  2. Below atmospheric pressure
  3. Equal to atmospheric pressure
  4. It is not possible to determine the pressure in the water.

ConcepTest Question

“nozzle 3”

Consider the flow from a firehose nozzle when the nozzle is in use. A1 and A2 represent the circular areas formed by the nozzle geometry. p1 and p2 represent the absolute pressures of the water at the surfaces indicated. One control volume that could be used to determine the net pressure force is the following:

In this case, the net pressure force in the x-direction is given by:

  1. p1*A1-p2*A2
  2. p1*A1-p2*A1
  3. p1*A2-p2*A2
  4. Need to know the area of the control volume parallel to A1 and A2.

Concept Test Question

“the unsteady term in the momentum equation 1”

Consider the tank that is filling in the figure below. The input flow is steady. The tank is not moving. The rate of change of the x-component of momentum in the tank is:

a.