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

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

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

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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 Unit: • P  power (W) • W  work (J) • t  time (s)

6. Power Equation • Another variation derived from : • P  power (W) • F  force (N) • v  velocity (m/s)

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 Air Resistance Engine Force 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)