1. CHAPTER 3 ENERGY

2. Common Units for Energy Joule Calorie Conversion: 1 calorie = 4.181 Joules

3. Type of Energy Potential Energy – the energy an object has due to its position Potential Energy (PE) = mgh PE = mass x acceleration due to gravity x height

4. Kinetic Energy Kinetic Energy = (1/2) mass x velocity 2 KE = (1/2) mv 2

5. Different Forms of Energy 1. Chemical Energy – E involved in chemical reactions 2. Mechanical Energy – E from machines 3. Electrical Energy – E from electromagnetic interactions 4. Nuclear Energy – E from the atom 5. Radiant Energy – E that travels through space (Ex. Infrared radiation = heat radiation; microwaves, light)

6. Law of Conservation of Energy Energy can neither be created or destroyed. It can only be converted from one form to another. The total energy remains constant.

7. Sources of Energy Sun (solar) Water (hydroelectric) Coal Biomass Petroleum Ocean Wind Hydrogen

8. WORK Work done on an object is defined as the product of force times the parallel distance through which the force acts. Work = force x distance W = Fd = mgd or = weight in lbs. x distance in feet (easier!) Remember that: Force = mass x acceleration due to gravity

9. 2 Requirements for WORK TO OCCUR 1. Something must move. 2. The movement must be in the same direction as the force applied. No work is done if you’re simply holding your phone. Lifting the phone to your ear means the phone travelled a certain distance, so work was done on the phone.

10. Units for Work ft-lb Joule newton-meter (kg-m/s 2 ) Conversion: 1 joule = 1 newton-meter = 1 kg-m 2 /s 2

11. Sample Problems (Easy) How much work is required to lift a 50 lb box vertically a distance of 2 ft? (Harder) How much work is required to lift a 50 kg. box vertically a distance of 2 meters?

12. POWER Is defined as work per unit time. Power = work time = w t Units of power: Joules/second watt Conversion: 1 J/s = 1 watt

13. Other unit for Power Horsepower (hp) Conversion: 1 hp = 746 watts (Note: Your electric bill is measured in kWH or kilowatt hours)