Chapter 6 Notes
Chapter Work Work is equal to the product of the magnitude of the displacement times the component of the force parallel to the displacement (in same direction) W=Fd or W=Fd cos Work (joule) = Force (newton) x distance (meters)
Chapter Kinetic Energy kinetic energy - energy of motion KE = _ mv 2 W net = KE 2 -KE 1 = KE Work-energy principle - The net work done on an object is equal to the change in its kinetic energy
Chapter Potential Energy potential energy - energy associated with position or configuration gravitational potential energy - PE =mgy or PE=mgh Work done by external force: W ext = PE 2 -PE 1 = PE Work done by gravity: W G = - PE
Chapter 6 Spring potential energy Spring force = - spring constant x displacement Fs = -kx Diagram pg. 156 Spring Elastic PE = _ kx 2
Chapter Conservative and Non- Conservative forces Conservative - work done does not depend on the path taken (gravity, elastic, electric) Non-Conservative - work done depends on the path taken (friction, air resistance, tension) Potential energy can only be defined for a conservative force.
Chapter 6 C-Conservative NC- Non-conservative W net = W C + W NC W C = - PE W NC = KE + PE
Chapter 6 Conservation of Mechanical Energy W NC = 0 no non-conservative forces present KE + PE = 0 for conservative forces only E = KE + PE KE 2 + PE 2 = KE 1 + PE 1 for conservative forces only
Chapter Problem solving using conservation of energy E = KE + PE = _ mv 2 +mgy When gravity only acts on object: _ mv 2 1 +mgy 1 = _ mv 2 2 +mgy 2 from top to bottom PE 1 =KE 2 Energy bucket pg. 160 Spring energy: _ mv _ kx 2 1 = _ mv _ kx 2 2
Chapter Conservation of Energy Read pg. 166 The total energy is neither increased nor decreased in any process. Energy can be transformed from one form to another, and transferred from one body to another, but the total amount remains constant.
Chapter Power Power is the rate at which work is done Power = work/time = energy transformed/time Power (watts) = work (joules)/ time (sec)