# Physics Lect 3

 Equilibrium (in Physics) no translational (straight line) or angular (rotational) accelerationtherefore: moving at a constant velocity* when a system is not in equilib, write it as if it were (i.e. Fup = Fdown) and then add "ma" to the side with less force (i.e. the direction it is moving in) Torque T = F lF: forcel : lever armTcw = Tccw * remember that the "mg" of objects acts at the center of gravity! Energy 1) Non Mechanical Energy 2) Mechanical Energy a) Kinetic K = 0.5 mv2 b) Potential ** i) Gravitational Ug = mgh** ii) Elastic Ue = 0.5 k Δx Work W = Fd cos θFriction changes the internal energy of an object and it is therefore a form of work (Not Heat)W = ΔK + ΔU + ΔEi Conservative Forces i.e. gravity, Hooke's Law, electo & magnetic field forcesΔ E is the same for any path!when only conservative forces are at work: 0 = ΔK + ΔU Nonconservative Forces kinetic friction, pushing/pulling forceswhen nonconservative forces are at work: W = ΔK + ΔU Power P = ΔE / tP = ΔW / tinstantaneous power due to force is Pinst = F v cosθ Friction as Work Fk d cosθ = ΔK + ΔU Authorlaskiru ID58868 Card SetPhysics Lect 3 DescriptionEquilibrium, Torque, & Energy Updated2011-01-10T03:37:01Z Show Answers