== UNIT 2: FORCE AND TRANSLATIONAL DYNAMICS ==
System: choose boundaries, internal forces cancel
External forces cause system acceleration
ΣF = ma (net force = mass x acceleration)
Free-body diagram: ONLY external forces on chosen object
Weight = mg (field force)
Normal force: contact perpendicular, NOT always equal to weight
Friction: kinetic = μ_k*F_N, static ≤ μ_s*F_N
Friction opposes motion, direction opposite velocity
Incline: resolve gravity into parallel (mg sin θ) and perpendicular (mg cos θ)
Tension: pulls along string/rope, same throughout ideal rope
Pulley: massless frictionless pulley transmits force unchanged
Newton's 3rd Law: action-reaction pairs equal opposite different objects
Mass vs weight: mass constant, weight depends on location
Equilibrium: ΣF = 0, not necessarily zero velocity
Terminal velocity: when drag = weight, a = 0, v constant