Lecture 5-6

Question 1

What is Fb representitive of?

Answer 1

Buoyancy force

Question 2

Fb =

Answer 2

Buoyant force =

ρf g (s+h) A - ρf g s A

density of the fluid x gravity x (depth + thickness) x area - density of ….. x …. x depth x …. x …..

Question 3

Resultant equation of Fb =

Answer 3

ρf g v

density of fluid x gravity x volume

Question 4

Magnitude of buoyant force must be equal to

Answer 4

weight of displaced fluid volume

Question 5

An immersed neutrally buoyant body is stable if

Answer 5

the center of the gravity is directly below the center of buoyancy of the body

Question 6

What it is called when the center of gravity and center of buoyancy is on the same point?

Answer 6

neutrally stable

Question 7

What is it called when the center of gravity is above the center of buoyancy force?

Answer 7

Unstable

Question 8

When an unstable body is submered in a fluid, what occurs?

Answer 8

It rotates using a restoring moment to get the center of gravity to be below the center of buoyant force

Question 9

Condition for floatation: buoyancy force =

Answer 9

weight of body

Fb = W

Question 10

How to use specific gravity of a material to work out whether a body will float or sink in a fluid?

Answer 10

Look at whether the specific gravity of the body is larger or smaller compared to the specific gravity of the fluid

Question 11

The metacenter is

Answer 11

a line linking the new center of buoyant force to the geometrical central line that cuts through the body

Question 12

When the metacenter point is above the center of gravity the body is said to be

Answer 12

stable

Question 13

When the metacenter point is below the center of gravity the body is said to be

Answer 13

unstable

there is an overturning moment

Question 14

A system is defined as

Answer 14

a collection of mass

Question 15

m sys = constant is called

Answer 15

mass conserved

Question 16

Energy conservation: change in E sys =

Answer 16

W net in + Q net in

Question 17

When analysing a control volume, you must account for

Answer 17

in & out flows

Question 18

(m cv) =

Answer 18

ρ (V cv)

density X volume of control volume

Question 19

Q =

Answer 19

A1 v1

Question 20

Q in fluid dynamics represents

Answer 20

volume flow rate

Question 21

Volume flow rate is directly represented with the equation ……. and can be simplified further to …..

Answer 21

ΔV / Δt = A1 v1

change in volume / change in time = area X velocity

Question 22

Mass flowrate is resolved by using the volume flow rate equation by….

Answer 22

m = ρ Q = ρ A v

density of fluid X volume flow rate = density of fluid X area flow through X velocity

Question 23

Equation that links the two inlets into a control volume and the rate of change of fluid mass in CV;

Answer 23

dmCV / dt = Σm in - Σm out

change in fluid mass in CV / change in time = flow rate of mass in - flow rate of mqws out

Question 24

In a steady flow system what can we assume about the inlet and outlet of the CV? Mass flow rate equation becomes?

Answer 24

that both flow rates of mass into and out of the system are equal so

m in - m out = 0

m in = m out

Question 25

Σm1 = Σm2 can be expanded to

Answer 25

Σ (ρ1 A1 v1) = Σ (ρ2 A2 v2)

Question 26

For incompressible flows —— is assumed as constant throughout

Answer 26

ρ - density of the fluid

Question 27

For incompressible flows how can we write the steady flow equation?

Answer 27

Σ (A1 v1) = Σ (A2 v2)