1. + Work and Power Chapter 10

2. + Definitions Energy: the ability to produce a change on an object or its environment Work: the process of changing energy Power: the rate of work being done

3. + Work Work: changing kinetic energy Since kinetic energy is motion, anytime something moves work is done on that object What causes motion? A Force!!

4. Hmmmmm… So if the force is strong in this one, does that mean he has to do a lot of work?

5. + Work Equation Work = Δ K Or Work = (force)(distance) Units of Work are Joules (J) This makes sense, since work is simply a change in energy

6. + Example #1 A person pulls a vacuum cleaner across a floor with a 50 N force applied at 30° to the floor for a distance of 3 m. How much work is the person doing on the vacuum cleaner?

7. Power You do not know the power of the dark side…

8. + Power Power: the rate work is done Power depends on: Work (directly proportional) Time (inversely proportional) Units for power are Watts (W) P = (W/t)

9. + Example #2 A 2000kg car starts from rest and accelerates to a final velocity of 20 m/s in 15 s. During this time the car covers 150 m. What is the average power generated by the engine during this acceleration?

10. + Horsepower Horsepower: a measure of power comparing output to a horse Developed to compare steam engines to horses as engine became popular – an early marketing tool! 1hp = 746 W

11. + Example #3 Using the info from Example #2, how many horsepower was the engine generating during the acceleration?

12. Homework Chapter 10 p 241-244 #18,20,21,26,28, 36,38,44 Do your homework, you will!