
Equilibrium (in Physics)
 no translational (straight line) or angular (rotational) acceleration
 therefore: moving at a constant velocity
 * when a system is not in equilib, write it as if it were (i.e. F_{up} = F_{down}) and then add "ma" to the side with less force (i.e. the direction it is moving in)

Torque
 T = F l
 F: force
 l : lever arm
 T_{cw} = T_{ccw}
 * 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 mv^{2}
 b) Potential
 ** i) Gravitational U_{g} = mgh
 ** ii) Elastic U_{e} = 0.5 k Δx

Work
 W = Fd cos θ
 Friction changes the internal energy of an object and it is therefore a form of work (Not Heat)
 W = ΔK + ΔU + ΔE_{i}

Conservative Forces
 i.e. gravity, Hooke's Law, electo & magnetic field forces
 Δ E is the same for any path!
 when only conservative forces are at work: 0 = ΔK + ΔU

Nonconservative Forces
 kinetic friction, pushing/pulling forces
 when nonconservative forces are at work: W = ΔK + ΔU

Power
 P = ΔE / t
 P = ΔW / t
 instantaneous power due to force is P_{inst} = F v cosθ

Friction as Work
F_{k} d cosθ = ΔK + ΔU

