PRESSURE in WATER F = force exerted by water against a 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  ] see 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 50% more dense Muscle slightly more dense

ARCHIMEDES Principle Upward buoyant F = to volume of displaced water 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 = Float CG and CB out of line F gravity pushes  while F buoyancy pushes  pitching effect results with CB

Conditional Floater True Floater lungs inflated = Floats lungs deflated= Sinks when “drown-proofing” 1. Exhale then Inhale 2. Long hold of air 3. CG close to CB 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 Figure 14.4 on page 457 does not seem to transfer training effect to land running due to SPECIFICITY in Training

RESISTIVE FORCES 1. Skin Friction 2. Profile Drag 3. Wave Drag

Skin Friction 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 see FIG 14.8 on page 464 Bow wave in Front Crawl allows breathing with reduced profile drag