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Unformatted text preview: CHP 10 // energy concepts: (Diagram) Energy into system [total energy E = K + U] Energy out of system // Conservation law for free-fall motion : K f + U gf = K i + U gi Launching pebble example // Kinetic and Potential energy: scalar, not vector; Units 1 joule = 1 J = 1 kgm 2 s 2 // Kinetic K = ½mv 2 ; Energy of motion; Depends on object’s speed; Always positive // Gravitational Potential U g = mgy; Energy of position; Depends on object’s position // complex probs : if surface is curved, can subdivide surface into many small straight-line segments; K f + U gf = K i + U gi ; for ANY frictionless surface; particle’s speed changes as it changes position // conservation of E mech : E mech = K + U; Sum remains constant // Basic Energy Model: 3 hypotheses 1) K is associated w/motion of particle and U is associated w/position 2) K can be transformed to U (vice versa) 3) Under some circumstances, E mech = K + U is conserved // Prob-solving strategy: Conservation of E mech : Model choose system w/o friction or other losses of E mech Visualize draw before & after pic, define symbols, known values, identify what you’re trying to find...
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This note was uploaded on 03/17/2011 for the course PHYSC 110 taught by Professor Johnson during the Spring '10 term at American.
- Spring '10