PRESSURE in WATER F force exerted by water

PRESSURE in WATER • F = force exerted by water against submersed body Ø A = area of that body over which F is applied Ø water pressure = mass of water above body Ø pressure with depth [weight of the water ] Ø 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

DENSITY Lower than Water Higher than Water ü Air ü Bone ü Fat ü Muscle

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

Positive Buoyancy Negative Buoyancy Figure 14. 2 b Figure 14. 2 c ü Net Forces 0 ü water WD than body ü body WD than water ü body WD due to more fat tissue ü Net Forces 0 ü water WD ü body WD due to less fat, more muscle

CB: Center of Buoyancy Ø center of the volume of displaced water Ø Force of buoyancy acts at CB Ø CG and CB co-linear > -----Ø CG and CB out of line > -----occurs due to Fgravity pushes while Fbuoyancy pushes Ø pitching effect results with rotation @

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

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

HYDRODYNAMIC RESISTIVE FORCES 1. ------- Drag or ------ Friction 2. ---- Drag 3. ------- Drag (not found in aerodynamics)

Skin Friction Ø aka Surface Drag Ø caused by water moving past surface of body Ø body surface roughness , with water viscosity Ø with smooth surface, tight “skin” Ø 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 ( Dwave ) Ø Bow waves act against forward moving body Ø caused by moving through or near water surface ØDwave with speed of body moving in water ØDwave with up and down motions of the body Ø Bow wave in Front Crawl allows breathing with reduced profile drag

FIG 14. 8 WAVE DRAG