This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Lecture 10 Purdue University, Physics 220 1 Lecture 10 Potential Energy and Energy Conservation PHYSICS 220 Lecture 10 Purdue University, Physics 220 2 Potential Energy • Work done by gravity is independent of path • W g = mg (y f y i ) =  ∆ PE g • Define PE g = mgy • Only the difference in potential energy is physically meaningful, i.e., you have the freedom to choose the reference (or zero potential energy) point. • Works for any CONSERVATIVE force • There is a fact, or if you wish, a law, governing natural phenomena that are known to date. There is no known exception to this law; it is exact, so far we know. The law is called conservation of energy; it states that there is a certain quantity, which we call energy, that does not change in manifold changes which nature undergoes. That is a most abstract idea, because it is a mathematical principle; it says that there is a numerical quantity, which does not change when something happens. It is not a description of a mechanism, or anything concrete; it is just a strange fact that we can calculate some number, and when we finish watching nature go through her tricks and calculate the number again, it is the same. Richard Feynman Lecture 9 Purdue University, Physics 220 3 Lecture 9 Purdue University, Physics 220 4 Energy • Energy is “conserved” meaning it can not be created nor destroyed – Can change form – Can be transferred • Total Energy of an isolated system does not change with time • Types – Kinetic Energy – Potential Energy – Rest Energy (E=mc 2 ) – Thermal Energy – … … • Units: Joule (J) = N m = kg m 2 / s 2 Lecture 10 Purdue University, Physics 220 5 Work by Variable Force W = F x ∆ x Work is the area under the F vs x plotW= ∆ PE s = 1/2 k x 2 Spring: F spring = k x Potential Energy: Lecture 10...
View
Full
Document
This note was uploaded on 04/10/2011 for the course PHYS 220 taught by Professor Chang during the Spring '09 term at Purdue.
 Spring '09
 CHANG
 Physics, Energy, Gravity, Potential Energy, Work

Click to edit the document details