1Work and EnergyChapter 4RELATIONSHIP ENERGY is the capacity to do WORK WORK is the means by which ENERGY is transferred from one object/system to another Same units of measure (J) Work done by the external forces acting on an object causes a change in energy of the objectWORK to increase ENERGY Sports / Human Movement~{ Concerned with changing the velocity of an object{ Changing V means changing KE{ More work done = greater energy change Similar to Impulse-Momentum{ Large change in KE requires a large F be applied over a long distanceExamples Throwing a ball{ Sequential use of limb segments Shot put{ Maximize displacement in the direction of force applicationWork to Decrease Energy Absorbing Energy  Muscles ~ negative work on limbs to absorb their energy{ Landing / Falling{ Surfaces Increase distance over which F acts{ Decreases average value of FConservation of Mechanical Energy No external Forces other than Gravity No work is done IF NO WORK IS DONE, MECHANICAL ENERGY IS CONSERVED Projectile motion2Power Rate of doing work{ How quickly or slowly work is done P = W / twhich can also be expressed as P = F * vPower in Biomechanics Maximize output – time it takes Force – Velocity Trade off{ Bicycle gears{ Stride length / Stride ratePower originates from the musclesYou must be familiar with power production characteristics of muscles!Muscles As muscle’s contraction V increases, maximum F of contraction decreases Which means? Vm * Fmax = Muscle Power Output Max P.O. occurs @ ½ muscle’s max contraction velocity Now explain examples from before…Power in Biomechanics Power is a constraint of movement Duration of activity influences the PO that can be sustained (ex: clean &