Chapter 5: Fluids and Solids

Question 1

Fluid definition:

Answer 1

has the ability to flow and conform to the shape of the container

Question 2

Solid definition:

Answer 2

does not flow and its rigidity helps it retain a shape independent of that of any container

Question 3

Liquids and gases are both:

Answer 3

fluids

Question 4

Density equation:

Answer 4

p = ^m/_v

a scalar quantity; units = ^kg/_m³ or ^g/_mL or ^g/_cm³

Question 5

How many liters are in a cubic meter?

Answer 5

1000

Question 6

Equation to determine the weight of any volume of a given substance:

Answer 6

W = ρVg

where p is the density and V is the volume of the substance

Question 7

Specific gravity:

Answer 7

the ratio of the density of a substance to that of pure water at 1 atm and 4 degrees Celsius; if it is less than one the object will float; if it is greater than one the object will sink

Question 8

Density of water:

Answer 8

1,000 ^kg/_m³ or 1 ^g/_cm³

Question 9

Pressure is:

Answer 9

the force per unit of area; it is exerted by a fluid on the walls of its container and on objects placed in the fluid

Question 10

Equation to determine pressure:

Answer 10

P = ^F/_A

where F is the normal force and A is the area; a scalar quantity; units = Pa = ^N/_m²

Question 11

Pressure conversions:

Answer 11

1.013 X 10⁵ Pa = 1 atm = 760 torr = 760 mmHg

Question 12

Absolute pressure is:

Answer 12

the sum of all pressure at a certain point within a fluid; it is equal to the pressure at the surface of the fluid (liquid or gas) plus the pressure due to the fluid itself

Question 13

Equation to determine absolute pressure:

Answer 13

P = P_o + ρgh

where P is the absolute pressure, P_o is the pressure at the surface, and ρgh is (density fluid above)(gravity)(height of submerged object below surface)

units = ^N/_m²

Question 14

Gauge pressure is:

Answer 14

the difference between the surface pressure and the absolute pressure

Question 15

Equation to determine gauge pressure:

Answer 15

P_g = P - P_atm = (P_o + ρgh) - P_atm

units = Pa

Question 16

Forces and fluids:

Answer 16

fluids can exert perpendicular forces, but cannot withstand shear forces

Question 17

On the MCAT, liquids are assumed to be:

Answer 17

incompressible and are ideal conservative systems

Question 18

Forces and solids:

Answer 18

solids can exert perpendicular forces and can withstand shear forces

Question 19

If mass is held constant in the density equation, what is the relationship between volume and density?

Answer 19

inverse

Question 20

During thermal expansion, what happens to density and volume?

Answer 20

density decreases as volume increases

Question 21

The pressure exerted by a gas against that walls of its container will always be:

Answer 21

perpendicular to the container walls

Question 22

Hydrostatics is:

Answer 22

the study of fluids at rest and the forces and pressures associated with standing fluids

Question 23

Pascal’s principle states that:

Answer 23

an applied pressure to an incompressible fluid will be distributed undiminished throughout the entire volume of the fluid; hydraulic machines operate based on this principle

Question 24

Equation of Pascal’s principle for incompressible fluids in containers:

Answer 24

P = ^F₁/_A1 = ^F₂/_A2

V = A₁d₁ = A₂d₂

W = F₁d₁ = F₂d₂

Question 25

Area of a piston:

Answer 25

πr²

(the surface of a piston is circular)

Question 26

Equation to determine the buoyant force on a floating object:

Answer 26

F_buoy = (V_{fluid displaced})(p_fluid)(g) = weight of the object

units = (kg)(^m/_s²)

Question 27

Equation to determine the buoyant force on a fully submerged object:

Answer 27

F_buoy = (V_{object submerged})(p_fluid)(g)

units = (kg)(^m/_s²)

Question 28

When an object is placed in a fluid, it will sink until:

Answer 28

the point at which the volume of displaced fluid exerts a force that is equal to the weight of the object

Question 29

An object’s specific gravity represented as a percentage directly indicates:

Answer 29

the percentage of the object’s volume that is submerged in the fluid

Question 30

The direction of buoyant force is always:

Answer 30

opposite the direction of gravity

Question 31

Surface tension results from:

Answer 31

cohesion (the attractive force that a molecule of liquid feels toward other molecules of the same liquid)

Question 32

Adhesion:

Answer 32

the attractive force a molecule of liquid feels toward the molecules of some other substance (causes a meniscus)

Question 33

A meniscus curved upward forms when:

Answer 33

the adhesive forces between the liquid and the container are greater than the cohesive forces of the liquid

Question 34

A backward meniscus forms when:

Answer 34

the adhesive forces between the liquid and the container are less than the cohesive forces of the liquid

Question 35

Viscosity is:

Answer 35

the resistance of a fluid to flow; can be thought of as fluid friction; the higher the viscosity, the slower the flow

Question 36

Low-viscosity fluids have low internal resistance and behave more like:

Answer 36

ideal fluids (which have no viscosity)

Question 37

SI unit of viscosity:

Answer 37

(N)(^s/_m²)

Question 38

The two types of fluid flow:

Answer 38

laminar (smooth and orderly) and turbulent (rough and disorderly)

Question 39

Equation to determine the critical velocity (Vc) of a fluid flowing through a tube:

Answer 39

v_c = ^N_Rη/_ρD

where N_R is a given constant; η is the viscosity of the fluid, ρ is the density of the fluid, and D is the diameter of the tube

units = ^m/_s

Question 40

Streamines:

Answer 40

indicate the pathway followed by fluid particles as they move; velocity vector always tangentil to streamline; streamlines never cross each other

Question 41

For a closed system, the volumetric rate of flow is:

Answer 41

constant and independent of changes in cross sectional area (the amount of water flowing past a point in a given amount of time is constant regardless of the width of the tube)

Question 42

Fluids move more quickly through — passages and more slowly through — passages.

Answer 42

more quickly through narrow passages and more slowly through wider passages (continuity equation)

Question 43

The continuity equation:

Answer 43

v₁A₁ = v₂A₂ = constant (the rate of flow)

Question 44

Bernouli’s equation (an expression of conservation of energy for a flowing fluid):

Answer 44

P₁ + ¹/₂ρv₁² + ρgy₁ = P₂ + ¹/₂ρv₂² + ρgy₂

Question 45

For horizontal flow, there is an inverse relationship between:

Answer 45

pressure and velocity

Question 46

Elasticity of solids:

Answer 46

a measure of the response of a solid to an application of pressure; depending on the particular way in which the pressure is exerted, the object may experience a change in length, volume, or lateral displacement known as shear

Question 47

Stress on a solid is:

Answer 47

a measurement of the pressure (F/A) applied to the solid

Question 48

Strain on a solid is:

Answer 48

the degree to which the solid deforms under pressure

Question 49

Equation to determine Young’s Modulus (perpendicular application of force):

Answer 49

Y = ^(F/A) / _(∆L/L)

it gives the change in length of a solid when a pressure is applied perpendicularly to it (compression or stretching)

Question 50

Elastic limits of a solid:

Answer 50

the degree to which an object can be compressed or stretched before it is permanently deformed or ruptured

Question 51

Yield strength of a solid is:

Answer 51

the point of shape change beyond which a material will not return to its original dimensions once the applied force is removed

Question 52

Ultimate strength of a solid is:

Answer 52

the point at which enough stress is applied to a solid object that it ruptures

Question 53

Equation to determine Shear Modulus (parallel application of force):

Answer 53

S = ^(F/A) / _(x/h)

where x is the lateral displacement and h is the vertical displacement

Question 54

In both Young’s modulus and Shear modulus, the ratio is:

Answer 54

^(stress) / _(strain)

stress is always represented as pressure (F/A)

Question 55

Equation to determine Bulk modulus (chage in volume due to pressure):

Answer 55

B = ^(F/A) / _(∆V/V)

where V is volume

Question 56

Relationship between the speed of sound and the Bulk modulus:

Answer 56

the speed of sound is proportional to the square root of the bulk modulus; sounds travel fastest through solids (highest bulk modulus) and slowest through gases (lowest bulk modulus)

Question 57

Bernoulli’s equation states the the sum of — and — will be constant between any two points in a closed system.

Answer 57

static pressure and dynamic pressure