Energy

1. Energy • Energy is the ability to do work • Energy is typically not seen • We observe energy in action as it is converted from one form to another

2. Types of Energy • Mechanical • Motion of objects • Heat • Heat is actually a measure of how much the atoms are moving in an object • Electromagnetic • Light & “radio” waves • Sound • Vibration of molecules in a pattern created by a source

3. Types of Energy • Electrical • Moving electrons • Magnetic • Attraction & repulsion of north and south poles • Chemical • Based on chemical reactions • Nuclear • Nuclear energy is created by two methods • Fusion – the joining of atoms to create a new atom • Fission – the splitting of an atom into parts

4. 2 Varieties of Most Types of Energy • Energy will come in one of two types • Potential – stored energy • Kinetic – energy in motion

5. Law of Conservation of Energy • Energy can neither be created nor destroyed • It can change form • Sound becomes mechanical in your ear • Chemical becomes electrical in a battery • Chemical becomes mechanical in your car engine

6. Work • When energy is used to do something, work is accomplished • Work = Force X Distance • W = FxD • Work is measured in Joules (J)

7. I lift a 2 kg book 2 meters into the air • I have done 40 J of work • As the book is held in the air at 2 meters, it has 40 J of potential energy • If I drop the book, it will do 40 J of work on the way to the floor

8. You try it . . . • How much work is done in when an elevator lifts a 70 kg person 20 m into the air? • W=f*d, f=m*a • F= (70 kg)(9.8 m/s2) • F=686 N • W=(686 N)(20 m) • W=13720 J

9. How much PE? • If the 70 kg person is now 20 m up, how much PE? • PE = mgh • PE = (70 kg)(9.8 m/s2)(20 m) • PE = 13720 J

10. Machines Transform Energy • Because energy is not created or destroyed • work input = work output • Sometimes some of the input is converted to sound or heat due to friction

11. Simple Machines

12. What is a machine • A machine is something that changes the magnitude (amount) or direction of a force • It does not make for less work, only makes the work easier!!

13. 6 Simple Machines • Incline Plane • Wedge • Screw • Lever • Pulley • Wheel & Axle

14. Incline Plane • This is a ramp • The slower the slope, the less force needed • The slower the slope, the more distance needed

15. Wedge • This is two incline planes put together • An axe, a knife, and the cutting part of scissors are all wedges • A wedge will separate material as it pushes through

16. Screw • A screw is an incline plane that is wrapped around a cylinder • Screws, bolts, and spiral staircases are all examples

17. Lever • A lever has two parts • The lever (the part that moves) • The fulcrum (the part or location that the lever moves around

18. Classes of Levers • Three classes of levers • 1st class – a seesaw • 2nd class – a wheelbarrow • 3rd class – a tennis racket

19. Pulley • A single pulley will change the direction of the force • Pulleys may be fixed or moveable • A set of pulleys working together is know as block and tackle

20. Wheel & Axle • As the wheel is turned by the effort, the axle will turn with more force • A winch and a rear bike tire are examples of wheel and axle

21. Mechanical Advantage • Mechanical Advantage (MA) is a measure of how much the force is multiplied