1. Work, Power & Energy Work, Power & Energy Explaining the Causes of Motion Without Newton (sort of)

2. Work lThe product of force and the amount of displacement along the line of action of that force. Units: ft. lbs (horsepower) Newtonmeter (Joule) e

3. 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

4. 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?

5. Calculate Work Table of Variables: Force = +1000 N Displacement = +0.8 m

6. Calculate Work Table of Variables: Force = +1000 N Displacement = +0.8 m Select the equation and solve:

7. - & + 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 l push off phase of a jump

8. - & + Work lPositive work is performed when the direction of the force and the direction of motion are the same

9. 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

10. Calculate Work Table of Variables Force = +1000 N Displacement = -0.8 m

11. Calculate Work Table of Variables Force = +1000 N Displacement = -0.8 m Select the equation and solve:

12. - & + Work lPositive 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

13. 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 = 1300 Nm lMultiply by the number of steps

14. Work on a stair stepper lWork = Fd lForce l Push on the step l???? lDisplacement l Step Height l8 inches l“Work” per step l ???N x.203 m = ???Nm

15. Work on a cycle ergometer lWork = Fd lForce l belt friction on the flywheel lmass ie 3 kg lDisplacement l revolution of the pedals lMonark: 6 m l“Work” per revolution

16. Work on a cycle ergometer lWork = Fd lForce l belt friction on the flywheel lmass ie 3 kg lDisplacement l revolution of the pedals lMonark: 6 m l“Work” per revolution l 3kg x 6 m = 18 kgm

17. Similar principle for wheelchair

18. …and for handcycling ergometer

19. Energy lEnergy (E) is defined as the capacity to do workEnergy l Many forms lNo more created, only converted lchemical, sound, heat, nuclear, mechanical lKinetic Energy (KE): l energy due to motion lPotential Energy (PE): l energy due to position or deformation

20. Power lThe rate of doing work l Work = Fd Units: Fd/s = J/s = watt

21. Calculate & compare power lDuring the ascent phase of a rep of the bench press, two lifters each exert an average vertical force of 1000 N against a barbell while the barbell moves 0.8 m upward lLifter A: 0.50 seconds lLifter B: 0.75 seconds

22. Calculate & compare power Lifter A Table of Variables F = 1000 N d = 0.8 m t = 0.50 s Lifter B

23. Power on a cycle ergometer lWork = Fd lForce: 3kg lDisplacement: 6m /rev l“Work” per revolution l 3kg x 6 m = 18 kgm l60 rev/min

24. Power on a cycle ergometer lWork = Fd lForce: 3kg lDisplacement: 6m /rev l“Work” per revolution l 3kg x 6 m = 18 kgm l60 rev/min 1 Watt = 6.12 kgm/min (How so??)

25. Compare “power” in typical stair stepping lWork = Fd lForce: Push on the step lconstant setting lDisplacement l Step Height: 5” vs 10” l0.127 m vs 0.254 m lstep rate l 56.9 /min vs 28.8 /min lTime per step l 60s/step rate Thesis data from Nikki Gegel and Michelle Molnar

26. Compare “power” in typical stair stepping lWork = Fd lForce: Push on the step lconstant setting lDisplacement l Step Height: 5” vs 10” l0.127 m vs 0.254 m lstep rate l 56.9 /min vs 28.8 /min

27. Compare “power” in typical stair stepping lWork = Fd lForce: Push on the step lconstant setting lDisplacement l Step Height: 5” vs 10” l0.127 m vs 0.254 m lstep rate l 56.9 /min vs 28.8 /min Results: VO 2 similar fast/short steps vs slow/deep steps