PRESSURE in WATER F = force exerted by water against submersed F = force exerted by water against submersed

body body A = area of that body over which F is applied A = area of that body over which F is applied water pressure = mass of water above bodywater pressure = mass of water above body pressure pressure with depth [ with depth [weight of the water weight of the water ] ] FIG D.6 on page 99FIG D.6 on page 99

WD: Weight Density of Water

Wt. Density (WD) = weight per unit volume Wt. Density (WD) = weight per unit volume Salt Water has more wt. density than fresh water Salt Water has more wt. density than fresh water

due to salt giving more mass to the waterdue to salt giving more mass to the water Water is Water is NOTNOT compressible / Air compressible / Air ISIS compressible compressible density of water does not change with depthdensity of water does not change with depth air density does change as follows:air density does change as follows:

altitude, altitude, temperature = temperature = density of air density of air

DENSITYLower than Water Higher than Water

AirAir

FatFat

Bone Bone 50% more dense50% more dense

MuscleMuscleslightly more denseslightly more dense

ARCHIMEDES Principle

Upward buoyant FUpward buoyant F= to volume of displaced water= to volume of displaced water

FloatingFloating- body Wt. Density = to OR - body Wt. Density = to OR << than water WD than water WD

SinkingSinking- body Wt. Density - body Wt. Density >> than water WD than water WD

FIG 14.2b Positive Buoyancy

FIG 14.2c Negative Buoyancy

Positive Buoyancy Negative BuoyancyFigure 14.2b Figure 14.2c

Net Forces Net Forces 00 water WD water WD than body than body body WD body WD than water than water body WD body WD due to more due to more

fat tissuefat tissue

Net Forces Net Forces 0 0 water WD water WD body WD body WD body WD body WD due to due to

less fat, more muscleless fat, more muscle

CB: Center of Buoyancy

center of the volume of displaced watercenter of the volume of displaced water Force of buoyancy acts at CBForce of buoyancy acts at CB CG and CB co-linear = FloatCG and CB co-linear = Float CG and CB out of line rotation occurs due to CG and CB out of line rotation occurs due to

FFgravitygravity pushes pushes while while FFbuoyancybuoyancy pushes pushes

pitching effect results with rotation @ CBpitching effect results with rotation @ CB

Conditional Floater True Floater

lungs inflated = Floatslungs inflated = Floats lungs deflated= Sinkslungs deflated= Sinks when “drown-proofing” when “drown-proofing” 1. Exhale then Inhale1. Exhale then Inhale2. Long hold of air2. Long hold of air3. CG close to CB3. CG close to CB

Floats with or without Floats with or without inflated lungsinflated lungs

fat content fat content fat concentrated near fat concentrated near

body’s CGbody’s CG CG and CB are in lineCG and CB are in line

no rotation about CB no rotation about CB

RUNNING IN WATER

a) feet on floor b) feet do not contact floor

Running in Water often used in therapy or for adaptive groupsoften used in therapy or for adaptive groups shallow water = shallow water = buoyancy buoyancy load on legs load on legs deep water = deep water = buoyancy buoyancy load on legs load on legs does not seem to transfer training effect to land does not seem to transfer training effect to land

running due to SPECIFICITY in Trainingrunning due to SPECIFICITY in Training

HYDRODYNAMIC RESISTIVE FORCES

1. Skin Friction1. Skin Friction

2. Profile Drag2. Profile Drag

3. Wave Drag (not found in aerodynamics)3. Wave Drag (not found in aerodynamics)

Skin Friction

aka Surface Dragaka Surface Drag caused by water moving past surface of bodycaused by water moving past surface of body body surface roughness , body surface roughness , with water viscosity with water viscosity with smooth surface, tight “skin”with smooth surface, tight “skin” leastleast significant Drag Force in swimming significant Drag Force in swimming

Profile Drag (aka Form Drag) Caused by body front edge pushing water apartCaused by body front edge pushing water apart size of front area = size of front area = Drag, Drag, speed = speed = Drag Drag Water flow slowed in front Water flow slowed in front pressure zone pressure zone Water speeds up in back Water speeds up in back pressure zone pressure zone Drag Drag with streamlining with streamlining

FIG 14.6 on page 461 and FIG 14.7 on page 462FIG 14.6 on page 461 and FIG 14.7 on page 462

Wave Drag ( Dwave ) Bow waves act against forward moving bodyBow waves act against forward moving body caused by moving through or near water caused by moving through or near water

surfacesurfaceDDwavewave with speed of body moving in water with speed of body moving in water

DDwavewave with up and down motions of the body with up and down motions of the body Bow wave in Front Crawl allows breathing with Bow wave in Front Crawl allows breathing with

reduced profile drag reduced profile drag

FIG 14.8

WAVE DRAG