Deck 12: Fluid Flow

Question 1

Consider a viscous fluid flowing through a cylindrical tube. If we reduce the area of the cross-section by half, how will the flow rate change?

A)The flow rate will double.
B)The flow rate reduces by half.
C)The flow rate will increase by 4 times.
D)The flow rate will decrease by 4 times.

Answer 1

The flow rate will decrease by 4 times.

Question 2

The continuity equation (ÄV/Ät = const) is a consequence of conservation of which of the following aspects?

A)energy
B)shape
C)mass
D)pressure

Answer 2

mass

Question 3

How will the force that is required to slide microscope slides past each other change if we reduce the separation between slides by 100 times, while retaining the velocity?

A)The force would need to increase by 100 times.
B)The force would need to decrease by 100 times.
C)The force would need to increase by 10 times.
D)The force would need to decrease by 10 times.

Answer 3

The force would need to increase by 100 times.

Question 4

Which of the following is a property of an ideal fluid?

A)viscosity
B)incompressibility
C)turbulent flow
D)density fluctuations

Question 5

A fluid flows at a rate of 30 L per minute through a pipe that has a cross-sectional radius of 2 cm. How will the flow change in the part of the pipe where the radius is constricted to half of its value?

A)The flow decreases to 15 L per minute.
B)The flow increases to 60 L per minute.
C)The flow decreases to 120 L per minute.
D)The flow stays the same.

Question 6

Which quantity is conserved when Ohm's law is applied to a blood vessel that has variable resistance along its length?

A)flow rate
B)pressure
C)speed
D)volume

Question 7

Blood flows through an artery that has a narrowing of its diameter by 15% due to clogging. How does the speed of blood change in the area with the constricted cross-section?

A)The speed increases by 1.38 times.
B)The speed decreases by 1.38 times.
C)The speed increases by 0.76 times.
D)The speed decreases by 0.76 times.

Question 8

Bernoulli's equation is a consequence of conservation of which of the following?

A)energy
B)shape
C)mass
D)pressure

Question 9

A pipe is delivering water at a rate of 25 L per minute. The diameter of the pipe opening is 2.0 cm. What is the speed of water flow?

A)0.03 m/s
B)1.3 m/s
C)20 m/s
D)332 m/s

Question 10

Which of these statements describes a flow rate?

A)change of volume with time
B)change of mass with time
C)change of density with time
D)change of velocity with time

Question 11

The human body prioritizes its oxygen supply via blood based on the relevance of the organ and metabolic demand. What is the correct order of priorities of these selected organs, ranked from the highest to the lowest?

A)heart, brain, kidneys, liver
B)brain, heart, liver, kidneys
C)brain and heart equal priority, kidneys, liver
D)brain, heart, kidneys and liver equal priority

Question 12

One of the terms in Bernoulli's equation is ½ ñv². Which of these quantities does it represent?

A)kinetic energy
B)kinetic energy per unit volume
C)kinetic energy change in time
D)pressure per unit volume

Question 13

Corn syrup flows through a tube with a radius of 2 cm and a length of 2 m, at a speed of 0.4 m/s. What is the pressure difference in the tube? (Viscosity of syrup is ç = 1.38 Pa s.)

A)22 kPa
B)2.2 Pa
C)2.2 × 10^-2 Pa
D)8.8 × 10^-4 Pa

Question 14

Poiseuille's law for flow of a fluid through a tube relates flow rate, drop of pressure over the length of the tube, velocity of the fluid, and radius of the tube. In which of the following situations would there be no pressure drop?

A)if flow rate is constant
B)if viscosity is zero (ideal fluid)
C)in the case of laminar flow
D)if the velocity of the fluid is constant

Question 15

A fluid is flowing through a tube with a diameter of 4 mm, a length of 40 cm, at a speed of 0.7 m/s. The pressure drop is 950 Pa. What is the viscosity of the fluid?

A)68 Ns/m²
B)1.7 × 10^-3 N s/m²
C)6.7 × 10^-3 N s/m²
D)6.7 × 10^-5 N s/m²

Question 16

Water flows at 3 m/s through a horizontal pipe where the pressure is 2.3 × 10⁵ Pa. Where the pipe constricts to a quarter of its original area, what is the pressure?

A)1.6 × 10⁵ Pa
B)2.2 × 10⁵ Pa
C)2.3 × 10⁵ Pa
D)3.1 × 10⁵ Pa

Question 17

If two liquids with different viscosities flow through tubes with identical parameters, how do their flow rates differ?

A)The fluid with the higher coefficient of viscosity has a lower flow rate.
B)The fluid with the higher coefficient of viscosity has a higher flow rate.
C)Their flow rates are identical because the tubes are identical.
D)We need additional information to answer this, such as the densities of the two fluids.

Question 18

The fluid flow rate is 1.1 L per minute, and the tube has a diameter of 4 mm and a length of 10 cm. What is the viscosity of the fluid if the pressure drops 5.3 Pa over the length of the tube?

A)5 Pa s
B)2 Pa s
C)0.2 Pa s
D)5 × 10^-2 Pa s

Question 19

Blood flows with a velocity of 0.22 m/s through an artery that has a narrowing of the diameter by 15% due to clogging. How does the pressure of the blood change in the area that has the constricted cross-section? The density of blood is ñ = 1060 kg/m³.

A)The speed increases by 73 Pa.
B)The speed decreases by 73 Pa.
C)The speed increases by 22 Pa.
D)The speed decreases by 22 Pa.

Question 20

Water flows through a pipe that widens out to double its original diameter. How does the speed of water change in the area with the wider cross-section?

A)The speed doubles.
B)The speed increases by four times.
C)The speed decreases by four times.
D)The speed decreases by two times.

Question 21

Flow rate is calculated as the area of the cross-section of a pipe times the velocity of a fluid, and the change of volume of the fluid in time.

Question 22

The equation of continuity applies only to fluids flowing in tubes, not to free falling fluid.

Question 23

The outer diameter of an aorta is d = 2.6 cm. The fraction of the total diameter attributed to the wall is 15%. If the speed of blood in the aorta is 0.22 m/s, what is the rate at which the heart is pumping blood into the aorta, in litres per minute?

Question 24

A higher number of blood cells affects the flow resistance of blood through blood vessels. Resistance varies as a function of pressure difference.

Question 25

How is it possible for birds to fly without flapping their wings (glide)? Which principle is responsible for this ability? How does the shape of the wing allow for gliding?

Question 26

A pipe of 50 mm diameter is used to supply water from the first to the second floor. The pressure in the pipe is 5.0 atm, and the speed of the water is 2.5 m/s. On the second floor, 4.5 m above, the pipe has a diameter of 30 mm. What is the speed and pressure in the narrower pipe?

Question 27

Reynolds number (Re) is a parameter introduced to determine whether the flow of a fluid is laminar or turbulent. It is given as Re = ñvd/ç, where ñ is the density of the fluid, v is the average speed of the fluid, d is the diameter of the tube, and ç is the viscosity coefficient of a fluid. What is the unit for Reynolds number?

A)kg/m s
B)kg m/s
C)kg m²/s²
D)Re has no units

Question 28

Narrowing the tube through which a viscous fluid flows to a third of its original radius will reduce the flow rate by a factor of 81.

Question 29

The main purpose of the high pressure blood system in the human body is to supply organs with oxygen.

Question 30

The continuity equation is valid for an ideal fluid but not for a Newtonian, real fluid.

Question 31

The capillaries in our circulatory system are blood vessels connected in a series.

Question 32

In a viscous fluid, the force needed to move two surfaces past each other increases as separation between the surfaces is reduced.

Question 33

An artery that is constricted due to accumulated plaque on the inner walls tends to stretch outward a little in a constricted part, due to blood flow.

Question 34

Laminar flow occurs only in an ideal dynamic fluid.

Question 35

When blood branches into two or more blood vessels (in parallel) with different resistances, and then recombines into a single blood vessel again, which quantity is conserved?

A)flow rate
B)pressure
C)speed
D)volume

Question 36

Figure 12.1 The figure shows a Venturi meter: connected tubes filled with an ideal fluid. The upper figure shows the fluid at rest, with the fluid shown by shading at the same height in a W-pipe. The lower figure shows moving fluid and uneven heights in a W-pipe.
Explain why the fluid, as shown by shading in Fig. 12.1, rises in the middle branch of the W-pipe when the fluid above it flows in the direction shown by the arrow. Which law explains this phenomenon?

Question 37

If you hold two papers at the top and let them hang vertically, parallel to each other, and blow fast air between them, will the papers spread apart or stick together?

Question 38

Arteriosclerosis is a constriction of the aorta due to plaque accumulated on the inner walls. An aneurysm is a widening of the aorta due to a weakening of the wall. In which of these two deformations will pressure on the walls increase, and in which will pressure decrease so much that it could close the aorta?

Question 39

When a tube does not change radius, the pressure of a fluid must remain constant throughout the tube.

Question 40

Bernoulli's equation states that an increase in the speed of an ideal fluid is accompanied by a drop in its pressure.

Question 41

Figure 12.5 The figure shows volume flow rate of two different fluids.
Analyze curve (2) in Fig. 12.5, which describes a volume flow rate of blood as a function of the pressure difference along the blood vessel. How could an allergy that would cause widening of blood vessels lower the speed of blood, leading to anaphylactic shock?

Question 42

What is the thickness of a honey (viscosity ç = 8 Pa s) between two 10-cm-diameter parallel plates so that a force of 5 N is needed to pull the plates past each other at a speed of 0.1 m/s?

Question 43

Figure 12.4 The figure shows flow of fluid through pipe A, branching into two identical pipes B and C with radii equal to half the radius of A, which reunite into a single pipe D.
What fraction of the fluid from pipe A flows through pipe B in Fig. 12.4?

Question 44

Figure 12.2 The figure shows pressures in vertical tubes due to flow of (a) an ideal fluid and (b) a real fluid.
How does the real fluid differ from the ideal fluid? Which law(s) show(s) that Fig. 12.2(a) applies to the ideal fluid? Which law explains the gradual drop of pressures in the vertical tubes in Fig. 12.2(b)?

Question 45

Figure 12.4 The figure shows flow of fluid through pipe A, branching into two identical pipes B and C with radii equal to half the radius of A, which reunite into a single pipe D.
In Fig. 12.4, pipe A has a radius of 2 cm, and pipes B and C are each 6.0 m long. Glycerine, with a coefficient of viscosity 1.5 N s/m², flows through the pipes at 30.0 cm/s. What is the drop in pressure that results from branching into two pipes?

Question 46

Figure 12.3 The figure shows pressures in vertical tubes due to flow of (a) real fluid through a tube of uniform cross-section, and (b) real fluid through a tube of uneven cross-section.
Which law or physical principle explains the gradual drop of pressures in vertical tubes in Fig. 12.3(a), and why is the height in the middle vertical tube lower than in the others?

Question 47

Figure 12.5 The figure shows volume flow rate of two different fluids.
Describe the difference in characteristics of the two fluids (1 and 2) for which the flow rate versus pressure differences curves are given in Fig. 12.5. Which of the two can represent the flow rate of blood?