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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. Types of Energy. Mechanical Motion of objects Heat Heat is actually a measure of how much the atoms are moving in an object Electromagnetic
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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
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
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
2 Varieties of Most Types of Energy • Energy will come in one of two types • Potential – stored energy • Kinetic – energy in motion
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
Work • When energy is used to do something, work is accomplished • Work = Force X Distance • W = FxD • Work is measured in Joules (J)
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
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
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
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
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!!
6 Simple Machines • Incline Plane • Wedge • Screw • Lever • Pulley • Wheel & Axle
Incline Plane • This is a ramp • The slower the slope, the less force needed • The slower the slope, the more distance needed
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
Screw • A screw is an incline plane that is wrapped around a cylinder • Screws, bolts, and spiral staircases are all examples
Lever • A lever has two parts • The lever (the part that moves) • The fulcrum (the part or location that the lever moves around
Classes of Levers • Three classes of levers • 1st class – a seesaw • 2nd class – a wheelbarrow • 3rd class – a tennis racket
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
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
Mechanical Advantage • Mechanical Advantage (MA) is a measure of how much the force is multiplied
