Fluids and Flotation Flashcards
A fluid is characterised as being a substance of _______ moving particles, that yield to the slightest _______. They move ________
- freely
- pressure
- readily
Flotation is the ability of a body to maintain a ________ position at the surface of the water
-stationary
Buoyancy is the force in water that lifts ______ and fights against _______
- upward
- gravity
buoyant forces include the ________ of the person acting on the water, and _____ forces
- weight
- fluid
to float, the maximum buoyant force will be _______ _____ or _______ ___ the weight of the body
- greater than
- equal to
________ 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
- Archimedes’
- equal to
- weight
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
- less than
- water
- specific
________ 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
- specific
- density
weight density = weight/ _______
-volume
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
- neutrally
- less than-you float
- greater than-you sink
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
- conditional
- float
- sink
Centre of _________ is defined as being the centre of volume of the body displacing the water
-buoyancy
your rotational axis in the water in at your ______ of ________. Your _______ of _______ can act as a torque around it
- centre
- buoyancy
- centre
- gravity
______ 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
-relative
fluid movement is resisted by the force of _____
-drag
_______ drag (no. 1) is caused by fluid rubbing along the surface of the body
-surface/skin friction
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
- fluid
- surface
to reduce surface drag you should:
- _______ flow velocity
- _______ surface area of the body
- ________ smoothness of the surface
- _________ viscosity of fluid
- decrease
- decrease
- increase
- decrease
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
-turbulence,
Profile/form drag is reduced by increasing ________ of the body and _______ the cross-sectional area perpendicular to the flow. this is ________
- streamlining
- decreasing
- relative
the third form of drag is _____ drag. This is created by the body moving at the interface between 2 fluids, causing ____
- wave
- waves
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
- speed
- vertical
- decrease
______ is the most important resistance, especially at faster speeds
-wave
the total resistive drag force is a combination of ________ and _______ and ______ drag
- surface
- profile
- wave
the propulsive forces are the ____ force directed forwards to propel the body through water
-drag
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
-profile
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
- boundary
- surface
if the relative flow is _____, then there is a laminar or streamline flow pattern
-slow
if relative flow is ______, then the boundary layer _________ and turbulence forms low pressure behind the object
- fast
- separates
where the boundary layer separates depends on the ________ of relative flow
-velocity
__________ number characterises fluid flow around an object and is used to determine if flow is laminar or _______
- Reynold’s
- turbulent
_________ 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
-critical
Reynolds number is dependent on:
- ______ of flow
- _______ of the sphere
- _________ properties of the fluid
- velocity
- diameter
- physical
______ density does not change
-water
air density is _________ by both air temp and humidity, but is ______ by air pressure
- decreased
- increased
air is ______ viscous than water
-less
increases in temperature ________ the viscosity of gasses, but _________ the viscosity of liquids
- increase
- decrease
Fluid life force is the component of force acting at ______ angles to drag. It is directed ____________ to the oncoming flow
- right
- perpendicular
________ 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
- Bernoulli’s
- low
- high
- differential
lift and drag are inversely ______
-proportional
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
-attack
The angle of release/______ is the angle the CoG’s instantaneous velocity vector makes at released, measured from horizontal
-projection
the angle of _______ is the angle formed between the main plane of the object and the horizontal ground
-attitude
the centre of ________ is the point at which the resultant (lift and drag), air forces act on the projectile
-pressure
lift can be produced by ______, which is called the ______ _______
this is due to the pressure zones created by the rotation of the ball
- spin
- Magnus Effect
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 ______
- forward
- spin
the surface rotation speed is determined by multiplying the rotation rate by the _____ of the sphere
-radius
the magnus force can cause changes in the flight path depending on side spin, back spin and ___ spin
-top
