1. POWER AP I chapter 6: section 6.10

2. CONCEPT CHECK The moon revolves around the Earth in a nearly circular path, kept there by the gravitational force exerted on it by Earth. Is work done by Earth’s gravitational field on the moon? A. Yes but it is positive work B. Yes but it is negative work C. No work is done

3. POWER  Rate at which work is done.  energy transformed/time  P=W/t  Unit: joules/sec=Watts (W)  Practical unit: Horsepower (hp) 1hp=746 W

4. POWER AND SPEED  The faster you do the work the greater the power output.  P=W/t=F”d/t  d/t = Vave  P=F*Vave

5. A 60KG JOGGER RUNS UP A LONG FLIGHT OF STAIRS IN 4.0S. THE VERTICAL HEIGHT IS 4.5M. ESTIMATE THE JOGGER’S POWER OUTPUT IN WATTS AND HP. P=W/t = F”d/t = (mg)dcos Ө/t Ө=0 why? P={(60kg*9.8m/s 2 )4.5m}/4.0s = 2600 W 2600W * 1hp/746 W = 0.88 hp