1. P H Y S I C S Chapter 4: Work and Energy Section 4F: Power

2. Power The rate at which work is done

3. Work vs. Power Student A Student B

4. Work vs. Power Power accounts for “how fast” work is done A B

5. Power Equation

7. Household Appliances 60W light bulb - 60W Toaster : 800-1500W Microwave : 600-1500W Dishwasher : 1200-1500W Washing Machine : 500W Vacuum Cleaner : 200-700W Clothes dryer : 4000W Ceiling Fan : 10-50W Hair Blow dryer : 1000W Laptop Computer : 20-50W Desktop Computer : 80-150W Cell Phone Charger: 3-5W iPod/iPad Charger: 10W

8. Horsepower 1 horsepower (hp) = 746 Watts

9. In-Class Problem #1 What force would a 300 hp engine have to produce to keep a vehicle at a steady 23 m/s against air resistance and friction? F = 9,730 N Engine Force Air Resistance Friction

10. In-Class Problem #2 A 300 kg crate needs to be hoisted to a height of 20 m. How long will a 1500 W crane motor take to do this? t = 40 s

11. Assignment Problem Set 4F 4E-4F Quiz (Non-Conservative Forces and Power)