Error 1 — N and mg as action-reaction: Most common NEET trap. N and mg both act on the same body. They are balanced forces (Newton's Second Law), not a Third Law pair.

Error 2 — $f_s$ = μ_s N always: Static friction self-adjusts. If $F_{applied}$ < μ_s N, then $f_s$ = $F_{applied}$, not μ_s N. Always compare first.

Error 3 — N = mg on inclined plane: On a slope, N = mg cos θ. Using mg gives wrong friction and net force calculations.

Error 4 — Centripetal force as extra force: Never add "centripetal force" as a separate arrow in FBD. It is the net inward force, provided by existing forces.

Error 5 — Lift: mixing up signs: Forgetting sign convention. Fix upward as positive throughout the entire problem. W' = m(g + a) for upward, m(g − a) for downward.

Error 6 — Using μ_s after motion starts: Once sliding begins, use $f_k$ = μ_k N. μ_s applies only before motion starts.

Error 7 — Atwood tension = weight of one mass: T ≠ $m_{1}$g and T ≠ $m_{2}$g. Correct: T = 2m_{1}$$m_{2}$$\frac{g}{m_{1}+m_{2}}, which lies between $m_{2}$g and $m_{1}$g.

Error 8 — Momentum conservation with friction: Momentum is conserved only if $F_{ext}$ = 0. Friction is an external force on a block; don't apply conservation when it acts.

Error 9 — "Heavier objects fall faster": All objects fall with the same acceleration g in vacuum. Weight mg cancels with mass m in F = ma → a = g, independent of mass.

Error 10 — Weight of person in orbit is zero: True weight (gravitational force mg) exists in orbit. Apparent weight is zero because the person is in free fall. Weight ≠ apparent weight.