ACTIONREACTION FORCES body segments exert a force environment
ACTION/REACTION FORCES Øbody segments exert a force Øenvironment delivers reaction force ØNewton’s Third Law Øfor every force applied on a body Øthat body applies an equal & opposite force
• T = F x FA • F is board reaction • FA is d • t is board recoil time
Internal Forces External Forces üwithin defined body übody free of support ümuscles contractions change body shape üc of g position üoutside defined body übody in contact ümuscle contractions change body position üc of g position CHANGED
Motive Forces Resistive Forces ücause Motion ümuscle, pull of gravity buoyancy üconcentric contraction üfriction üfluid lift üoppose/resist Motion ümuscle, connective tissue üeccentric contraction ü friction üfluid drag
FORCE and PRESSURE ØForce - push, pull, blow, rub that changes a body’s motion or shape Øpressure - amount of force acting over area Øp & F direct relationship, p & A indirect
FRICTION FORCE üForce created between 2 contacting surfaces ücan be a Motive or a Resistive Force ütexture of surfaces [rough = more friction] üforce pressing together the 2 surfaces üsize of surface area NOT a factor ühigh coefficient of friction = low slippage
CENTRIPETAL FORCE üCenter seeking üforces rotating body to stay on a circular path üif Fc is insufficient, body will leave path on a tangent
ELASTIC FORCE üRecoil ability ümeasure of how quickly reformation follows deformation ücoefficient of elasticity = square root of rebound ht/dropped ht ühigh e = faster reforming
BUOYANCY FORCE ü upward lift Force on a body immersed in a fluid ü Archimedes Principle ü upward buoyant F = wt of volume of water displaced ü Negative Buoyancy - body wt. greater than the wt. of the volume of water displaced
POWER ØP = Force x velocity ØP = Force x distance/time
ENERGY: the ability to do work Kinds of Energy 1. chemical 2. electrical 3. heat 4. mechanical 3 types of Mechanical E 1. Elastic 2. Gravity - Potential 3. Kinetic
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