Mnemonic 1: MMKE — Collision Conservation

Momentum Must (conserved in ALL collisions) KE only when Elastic (KE conserved ONLY in elastic)

Use: Whenever you see a collision problem, start with: "Momentum always. KE? Only if elastic."

Mnemonic 2: "String 5, Rod 4"

String bottom: $\sqrt{5gR}$ — String = 5 Rod bottom: $\sqrt{4gR}$ — Rod = 4 String top: $\sqrt{gR}$ — String needs speed Rod top: 0 — Rod can rest

Memory sentence: "A 5-year-old needs to be held by a string, a 4-year-old can stand on a rod."

Mnemonic 3: WAFDKE — Work-Energy Theorem

Work by All Forces = Delta KE

Applied force + Friction + Gravity + Normal = $KE_{final}$ − $KE_{initial}$

Memory: "When ALL Forces Do, KE Evolves"

Mnemonic 4: "FDC" for Work Formula

Force × Displacement × Cosine(theta)

W = F × d × Cos θ

Mnemonic 5: Conservative Forces = "GEM"

Gravity, Elastic (spring), Magnetic (static fields) All others (friction, air drag) are non-conservative.

Mnemonic 6: Tension Difference = 6mg

$T_{bottom}$ − $T_{top}$ = 6mg — remember "hex" (6 sides) at the bottom vs. top.