This preview shows pages 1–6. Sign up to view the full content.
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 9 Purdue University, Physics 220 1 Lecture 9 Work and Kinetic Energy PHYSICS 220 Lecture 9 Purdue University, Physics 220 2 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 9 Purdue University, Physics 220 3 Work and Energy θ • Work: Transfer of Energy by Force W =  F   ∆ r  cos θ • Kinetic Energy (Energy of Motion) KE = 1/2 mv 2 • WorkKinetic Energy Theorem: Σ W = ∆ KE Lecture 9 Purdue University, Physics 220 4 Work by Constant Force • Only component of force parallel to direction of motion does work! W = F ∆ r cos θ F θ ∆ r F W F > 0: 0< θ < 90 : cos( θ ) > 0 ∆ r F W F = 0: θ =90 : cos( θ ) =0 ∆ r F W F < 0: 90< θ < 270 : cos( θ ) < 0 ∆ r F W > 0: 0< θ < 90 : cos( θ ) > 0 Lecture 9 Purdue University, Physics 220 5 Work by Constant Force • Example: You pull a 30 N chest 5 meters across the floor at a constant speed by applying a force of 50 N at an angle of 30 degrees. How much work is done by the 50 N force?...
View
Full
Document
This note was uploaded on 04/23/2011 for the course PHYS 220 taught by Professor Chang during the Spring '09 term at Purdue University.
 Spring '09
 CHANG
 Energy, Kinetic Energy, Work

Click to edit the document details