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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. Fup = Fdown) and then add "ma" to the side with less force (i.e. the direction it is moving in)
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Torque
- T = F l
- F: force
- l : lever arm
- Tcw = Tccw
- * remember that the "mg" of objects acts at the center of gravity!
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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
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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 + ΔEi
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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
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Nonconservative Forces
- kinetic friction, pushing/pulling forces
- when nonconservative forces are at work: W = ΔK + ΔU
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Power
- P = ΔE / t
- P = ΔW / t
- instantaneous power due to force is Pinst = F v cosθ
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Friction as Work
Fk d cosθ = ΔK + ΔU
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