Fluids and Flotation

Question 1

A fluid is characterised as being a substance of _______ moving particles, that yield to the slightest _______. They move ________

Answer 1

• freely
• pressure
• readily

Question 2

Flotation is the ability of a body to maintain a ________ position at the surface of the water

Answer 2

-stationary

Question 3

Buoyancy is the force in water that lifts ______ and fights against _______

Answer 3

• upward

- gravity

Question 4

buoyant forces include the ________ of the person acting on the water, and _____ forces

Answer 4

• weight

- fluid

Question 5

to float, the maximum buoyant force will be _______ _____ or _______ ___ the weight of the body

Answer 5

• greater than

- equal to

Question 6

________ Principle stated that a body that is totally or partially immersed in fluid will experience an upward buoyant force that is _______ ___ the _____ of the volume of fluid displaced by that body

Answer 6

• Archimedes’
• equal to
• weight

Question 7

In order to float: the weight of the body must be ____ ____ of equal to the weight of equal volume of _____
this equals the ______ gravity of a body

Answer 7

• less than
• water
• specific

Question 8

________ gravity is the measure of the _________ of an object (and therefore it’s ability to float)
this depends on composition of fat/muscle/bone/air

Answer 8

• specific

- density

Question 9

weight density = weight/ _______

Answer 9

-volume

Question 10

3 types of buoyancy:

• __________ buoyant is when the body density = the water density
• positively buoyant is when the body density is ____ than the water density
• negatively buoyant is when the body density is ___ than the water density

Answer 10

• neutrally
• less than-you float
• greater than-you sink

Question 11

The 3 types of floaters include __________, which depends on inspiration, true floaters, where you ______ no matter inspiration, and true sinkers, where you _______ no matter inspiration

Answer 11

• conditional
• float
• sink

Question 12

Centre of _________ is defined as being the centre of volume of the body displacing the water

Answer 12

-buoyancy

Question 13

your rotational axis in the water in at your ______ of ________. Your _______ of _______ can act as a torque around it

Answer 13

• centre
• buoyancy
• centre
• gravity

Question 14

______ motion is the direction and speed of fluid flowing part a moving object. These future are determined by the velocity of the object and the option of surrounding fluid

Answer 14

-relative

Question 15

fluid movement is resisted by the force of _____

Answer 15

-drag

Question 16

_______ drag (no. 1) is caused by fluid rubbing along the surface of the body

Answer 16

-surface/skin friction

Question 17

surface drag depends on the _____ involved, the velocity of flow relative to that body, the ______ area of the body and the smoothness of the body

Answer 17

• fluid

- surface

Question 18

to reduce surface drag you should:

• _______ flow velocity
• _______ surface area of the body
• ________ smoothness of the surface
• _________ viscosity of fluid

Answer 18

• decrease
• decrease
• increase
• decrease

Question 19

Profile/Form drag is caused by __________ created by an object moving through a fluid. It depends on how much of the body is perpendicular to the flow and the shape of the body

Answer 19

-turbulence,

Question 20

Profile/form drag is reduced by increasing ________ of the body and _______ the cross-sectional area perpendicular to the flow. this is ________

Answer 20

• streamlining
• decreasing
• relative

Question 21

the third form of drag is _____ drag. This is created by the body moving at the interface between 2 fluids, causing ____

Answer 21

• wave

- waves

Question 22

wave drag is dependent upon the _____ of the swimmer and the amount of ________ movement (bobbing up and down). decreasing both of these will _______ wave drag

Answer 22

• speed
• vertical
• decrease

Question 23

______ is the most important resistance, especially at faster speeds

Answer 23

-wave

Question 24

the total resistive drag force is a combination of ________ and _______ and ______ drag

Answer 24

• surface
• profile
• wave

Question 25

the propulsive forces are the ____ force directed forwards to propel the body through water

Answer 25

-drag

Question 26

turbulence creates an area of low pressure where it occurs (usually behind you) and so naturally, the high pressure on the other side wants to move across to even it out. This is what we experience as ______ drag and is where you are sucked backwards

Answer 26

-profile

Question 27

the ______ layer is the layer of fluid that is carried on the ______ of any object going through. This layer then tugs on the next outside layer of fluid and so on, resulting in _______ drag

Answer 27

- boundary | - surface

Question 28

if the relative flow is _____, then there is a laminar or streamline flow pattern

Answer 28

-slow

Question 29

if relative flow is ______, then the boundary layer _________ and turbulence forms low pressure behind the object

Answer 29

- fast | - separates

Question 30

where the boundary layer separates depends on the ________ of relative flow

Answer 30

-velocity

Question 31

__________ number characterises fluid flow around an object and is used to determine if flow is laminar or _______

Answer 31

- Reynold's | - turbulent

Question 32

_________ Reynold's number is broken into 5 sections: - when R<1: type 1, we have laminar flow - when R approx = 1: transition to type 2 - when 1 200,000: fully turbulent flow, and form drag dominates

Answer 32

-critical

Question 33

Reynolds number is dependent on: - ______ of flow - _______ of the sphere - _________ properties of the fluid

Answer 33

- velocity - diameter - physical

Question 34

______ density does not change

Answer 34

-water

Question 35

air density is _________ by both air temp and humidity, but is ______ by air pressure

Answer 35

- decreased | - increased

Question 36

air is ______ viscous than water

Answer 36

-less

Question 37

increases in temperature ________ the viscosity of gasses, but _________ the viscosity of liquids

Answer 37

- increase | - decrease

Question 38

Fluid life force is the component of force acting at ______ angles to drag. It is directed ____________ to the oncoming flow

Answer 38

- right | - perpendicular

Question 39

________ principle states that where the flow velocity is fast, the pressure is ____ and where the flow velocity is slow, the pressure is ____ This creates a pressure ________, where the force is directed from high to low pressure zones

Answer 39

- Bernoulli's - low - high - differential

Question 40

lift and drag are inversely ______

Answer 40

-proportional

Question 41

the angle of ______ is the angle between the main plane of the object and the flow direction. It has to be in the correct orientation to ensure lift is produced and not drag

Answer 41

-attack

Question 42

The angle of release/______ is the angle the CoG's instantaneous velocity vector makes at released, measured from horizontal

Answer 42

-projection

Question 43

the angle of _______ is the angle formed between the main plane of the object and the horizontal ground

Answer 43

-attitude

Question 44

the centre of ________ is the point at which the resultant (lift and drag), air forces act on the projectile

Answer 44

-pressure

Question 45

lift can be produced by ______, which is called the ______ _______ this is due to the pressure zones created by the rotation of the ball

Answer 45

- spin | - Magnus Effect

Question 46

Magnus forces depends on the ratio between the surface rotation speed and the ____ speed of the ball. it also depends on air density, the mass of the sphere, the smoothness and the amount of ______

Answer 46

- forward | - spin

Question 47

the surface rotation speed is determined by multiplying the rotation rate by the _____ of the sphere

Answer 47

-radius

Question 48

the magnus force can cause changes in the flight path depending on side spin, back spin and ___ spin

Answer 48

-top