Lecture 3

Question 1

floating object mass

Answer 1

mass of object= mass of fluid displaced

Question 2

submerged object volume

Answer 2

volume of object equals volume of fluid displaced

Question 3

Specific gravity

Answer 3

density of substance compared to density of water

Question 4

Specific gravity <1

Answer 4

substance is lighter than water

Question 5

density of water

Answer 5

1000 kg m3= 1g/cm3

Question 6

Pascals principle

Answer 6

pressure applied anywhere in an enclosed incompressible fluid will be distributed undiminished throughout the fluid

Question 7

absolute pressure

Answer 7

pressure of system relative to a vacuum

Pab= Pguage + Patm

Question 8

gauge pressure

Answer 8

amount by which a systems. pressure deviates from atmospheric pressure

Question 9

hydraulic lift

Answer 9

2 pistons with a container containing incompressible liquid. Force on piston 1 applied pressure and is transferred to piston 2

Piston 2 has greater area so it has greater force (P is constant)

Pascals

Question 10

Buoyant force

Answer 10

fluid exerting force on an object that is in fluid

Pressure and force increases as depth increases.

Different pressure and force at different depth= increased Buoyant force

Question 11

When is buoyant force high

Answer 11

when the object is fully submerged

Question 12

Buoyancy equation

Answer 12

Fb= (Density fluid) (V fluid) g

Fb= mass of fluid * g

Question 13

Archimedes principle

Answer 13

upward buoyant force is equal in magnitude to the eight of displaced fluid

Question 14

Floating object forces

Answer 14

displaces volume of fluid with mass equal to its own mass

Fb= gravitational force (weight)

weight object is cancelled by weight of fluid displaced

Question 15

Fraction of object submerged when floating

Answer 15

V fluid/ V object

density object/ density fluid

equals Specific gravity

Question 16

submerged object forces

Answer 16

displaced a volume of fluid equal to its own volume, experiences an upward Fb equal to Gravitational force

V fluid and depth are at max

m object= m fluid, V fluid= V object

(Fraction of object submerged= 1- equal density)

Question 17

Sunk object forces

Answer 17

Fb is smaller than downward gravitational force

displaced volume equal to own object volume

M fluid < M object, V fluid= V object

Object is denser

Fb + FN = Fg= M object G

Question 18

Weight loss of sunken object

Answer 18

density fluid / density object x 100%

Question 19

floating object equation

Answer 19

Fb= M(fluid)g = Fg= M(object) g

Question 20

Ideal fluid traits

Answer 20

• no viscosity
• incompressible with uniform density
• lack turbulence (steady, laminar flow, same velocity at any point)
• have irrotational flow ( does not rotate as it flows)

Question 21

What does the continuity equation mean

Answer 21

volume is constant, and equals A*d

same volume flows through in a given time, it has a rate equal to Q

Narrow pipe= greater velocity

Question 22

Continuity equation

Answer 22

Q= Av

Q= volume flow rate

v=velocity= d/t

Question 23

Mass flow rate

Answer 23

I= density (Q) = density(A)(v)

Question 24

stream lines

Answer 24

show ideal fluid

velocity is tangent to line

closer streamlines means greater velocity

Question 25

Bernoullis equation

Answer 25

p1+(1/2ρv1^2)+ρgh1 =p2+(1/2ρv2^2)+ ρgh2

h= distance above arbitrary point

Question 26

Velocity of fluid from a spigot

Answer 26

V= sqrt (2gh)

Question 27

Pitot tube

Answer 27

u shaped tube. Opening 1 has velocity= 0, pressure=static

opening 2 has moving fluid, pressure= total fluid pressure

shows velocity of fluid moving around it

Question 28

venturi tube

Answer 28

horizontal tube with constricted region

shows velocity of fluid flowing in it

decreased A means increased V, decrease in pressure

Question 29

Venturi effect

Answer 29

decrease in pressure when fluid flows through constricted pie

Question 30

pitot tube equation

Answer 30

h1=h2, v1=0, so

P2+ 1/2ρv2^2= P1

Question 31

Real fluid characteristics

Answer 31

velocity is greatest at center of the pipe

resistance to flow increases as length of pipe increases, more narrow= more drag effect (volume effect)

Volume= pi r^2 d

Question 32

Real fluid flow

Answer 32

delta p= QR

fluid flows high to low pressure

Question 33

Poiseuilles Law

Answer 33

Q= delta P [(pi r^4)/ 8 nL]

n= viscosity, L= pipe length

for horizontal pipe with constant area

increase in radius can increase flow rate

Question 34

How does velocity change with radius

Answer 34

smaller radius means increase in velocity

Question 35

Surface tension

Answer 35

intensity of intermolecular force of fluid per length

higher temperature means weaker tension

Question 36

cohesive vs. adhesive forces

Answer 36

cohesive act in surface tension, adhesive act between a tube and fluid molecules

Question 37

concave vs convex

Answer 37

concave is when adhesive forces are stronger (fluid pulled upward at end)

in convex, cohesive is stronger (fluid pulled downward at ends)