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ACTION/REACTION FORCES

ACTION/REACTION FORCES. body segments exert a force environment delivers reaction force Newton’s Third Law for every force applied on a body that body applies an equal & opposite force. T = F x FA F is board reaction FA is d  t is board recoil time. within defined body

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ACTION/REACTION FORCES

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  1. ACTION/REACTION FORCES • body segments exert a force • environment delivers reaction force • Newton’s Third Law • for every force applied on a body • that body applies an equal & opposite force

  2. T = F x FA • F is board reaction • FA is d  • t is board recoil time

  3. within defined body body free of support muscles contractions change body shape c of g positionNOT changed outside defined body body in contact muscle contractions change body position c of g position CHANGED Internal Forces External Forces

  4. cause Motion muscle, pull of gravity buoyancy concentric contraction friction fluid lift oppose/resist Motion muscle, connective tissue eccentric contraction friction fluid drag Motive Forces Resistive Forces

  5. FORCE and PRESSURE • Force - push, pull, blow, rub that changes a body’s motion or shape • pressure - amount of force acting over area • p & F direct relationship, p & A indirect

  6. FRICTION FORCE • Force created between 2 contacting surfaces • can be a Motive or a Resistive Force • texture of surfaces [rough = more friction] • force pressing together the 2 surfaces • size of surface area NOT a factor • high coefficient of friction = low slippage

  7. CENTRIPETAL FORCE • Center seeking • forces rotating body to stay on a circular path • if Fc is insufficient, body will leave path on a tangent

  8. ELASTIC FORCE • Recoil ability • measure of how quickly reformation follows deformation • coefficient of elasticity = square root of rebound ht/dropped ht • high e = faster reforming

  9. BUOYANCY FORCE • upward lift Force on a body immersed in a fluid • Archimedes Principle • upward buoyant F = wt of volume of water displaced • Negative Buoyancy - body wt. greater than the wt. of the volume of water displaced

  10. POWER • P = Force x velocity • P = Force x distance/time

  11. Kinds of Energy 1. chemical 2. electrical 3. heat 4. mechanical 3 types of Mechanical E 1. Elastic 2. Gravity - Potential 3. Kinetic ENERGY: the ability to do work

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