Lect10 - PHYS 172 Modern Mechanics Lecture 10 The Energy...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Fall 2011 PHYS 172: Modern Mechanics Lecture 10: The Energy Principle Read 6.1 – 6.7 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
TODAY • The Energy Principle • Energy is Conserved • Rest Energy and Kinetic Energy • Work = ! F ! " ! r 2
Background image of page 2
What Is Energy? Energy is just some number you can compute that obeys a conservation law. It ` s helpful book-keeping. (See Feynman Lectures on Physics, Vol. 1, Sec. 4-1) Why Introduce Energy? • say something about initial and final states of a system • predict whether some process CAN occur Without following the details of a complicated process, we can: Basically, for some problems, using energy is much simpler than using the momentum principle . Often, however, we ` ll use both principles in combination. 3
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The Energy Principle system surr E W Q ! = + l effect z l cause z (due to interactions) Compare With Momentum Principle: impulse syst m net e F p t = ! ! = ! ! l effect z l cause z (due to interactions) NOTE: Momentum is a vector. Energy is a scalar (no direction). * We mean the Work done ON a System by a Force in the Surroundings* 4
Background image of page 4
Energy is A Conserved Quantity 0 system surroundings E E ! + ! = Compare with Conservation of Momentum: 0 system surroundings p p ! + ! = ! !
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 21

Lect10 - PHYS 172 Modern Mechanics Lecture 10 The Energy...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online