Work lThe product of force and the amount of displacement along the line of action of that force. Units: Joule (J)

Work = F x d To calculate work done on an object, we need: The Force ¬The average magnitude of the force ­The direction of the force The Displacement ¬The magnitude of the change of position ­The direction of the change of position

Calculate Work lDuring the ascent phase of a rep of the bench press, the lifter exerts an average vertical force of 1000 N against a barbell while the barbell moves 0.8 m upward lHow much work did the lifter do to the barbell?

Calculate Work Table of Variables: Force = N Displacement = +0.8 m Force is positive due to pushing upward Displacement is positive due to moving upward

Calculate Work Table of Variables: Force = N Displacement = +0.8 m Select the equation and solve:

- & + Work lPositive work is performed when the direction of the force and the direction of motion are the same l ascent phase of the bench press l Throwing a ball l push off (upward) phase of a jump

Calculate Work lDuring the descent phase of a rep of the bench press, the lifter exerts an average vertical force of 1000 N against a barbell while the barbell moves 0.8 m downward

Calculate Work Table of Variables Force = N Displacement = -0.8 m Force is positive due to pushing upward Displacement is negative due to movement downward

Calculate Work Table of Variables Force = N Displacement = -0.8 m Select the equation and solve:

- & + Work lNegative work is performed when the direction of the force and the direction of motion are the opposite l descent phase of the bench press l catching l landing phase of a jump

Work performed climbing stairs lWork = Fd lForce l Subject weight lFrom mass, ie 65 kg lDisplacement l Height of each step lTypical 8 inches (20cm) lWork per step l 650N x 0.2 m = Nm lMultiply by the number of steps

Work-energy theorem: Net work = ΔKE l The net external work done on an object equals its change in kinetic energy. This theorem can be proved in relatively few algebra steps from the definitions of work and kinetic energy. ΔKE is the final KE minus the initial KE.

Power lThe rate of doing work l Work = Fd Units: Watt (W)