PRESSURE in WATER F = force exerted by water against submersed body  A = area of that body over which F is applied  water pressure = mass of water above body  pressure  with depth [ weight of the water  ]  FIG D.6 on page 99

WD: Weight Density of Water Wt. Density (WD) = weight per unit volume Salt Water has more wt. density than fresh water due to salt giving more mass to the water Water is NOT compressible / Air IS compressible density of water does not change with depth air density does change as follows:  altitude,  temperature =  density of air

DENSITY Lower than Water Higher than Water Air Fat Bone Muscle

ARCHIMEDES Principle  Upward buoyant F = to volume of  Floating - body Wt. Density = to OR < than water WD  Sinking - body Wt. Density > than water WD

Positive Buoyancy Negative Buoyancy Figure 14.2b Figure 14.2c Net Forces  0 water WD  than body body WD  than water body WD  due to more fat tissue Net Forces  0 water WD  body WD  body WD  due to less fat, more muscle

CB: Center of Buoyancy  center of the volume of displaced water  Force of buoyancy acts at CB  CG and CB co-linear >  CG and CB out of line > occurs due to F gravity pushes  while F buoyancy pushes   pitching effect results with CB

Conditional Floater True Floater lungs inflated = Floats lungs deflated= Sinks Floats with or without inflated lungs fat content  fat concentrated near body’s CG CG and CB are in line  no rotation about CB

Running in Water  often used in therapy or for adaptive groups  shallow water =  buoyancy  load on legs  deep water =  buoyancy   load on legs  does not seem to transfer training effect to land running due to SPECIFICITY in Training

HYDRODYNAMIC RESISTIVE FORCES Drag or Friction Drag Drag (not found in aerodynamics)

Skin Friction  aka Surface Drag  caused by water moving past surface of body   body surface roughness,  with water viscosity   with smooth surface, tight “skin”  least significant Drag Force in swimming

Profile Drag (aka Form Drag) Caused by body front edge pushing water apart  size of front area =  Drag,  speed =  Drag Water flow slowed in front   pressure zone Water speeds up in back   pressure zone Drag  with streamlining FIG 14.6 on page 461 and FIG 14.7 on page 462

Wave Drag ( D wave )  Bow waves act against forward moving body  caused by moving through or near water surface  D wave  with speed of body moving in water  D wave  with up and down motions of the body  Bow wave in Front Crawl allows breathing with reduced profile drag

FIG 14.8 WAVE DRAG