Pattern 1: Action-Reaction Pair Identification (Conceptual, 1 mark)

Frequency: Nearly every year Format: Four options showing force pairs; one is a true Newton's Third Law pair Trap: N and mg on the same body; students confuse balanced forces with action-reaction pairs Strategy: Check — do the two forces act on DIFFERENT bodies? If not, it's not a Third Law pair.

Pattern 2: Apparent Weight in a Lift (Numerical, 1 mark)

Frequency: 2–3 times per 5 years Format: Mass of person given, acceleration of lift given; find scale reading Trap: Forgetting to check direction of acceleration; confusing "moving upward" with "accelerating upward" Strategy: Always fix upward as positive. W' = m(g + a) for upward acceleration, m(g − a) for downward.

Pattern 3: Self-Adjusting Static Friction (Conceptual/Numerical, 1 mark)

Frequency: Common Format: Block on surface, applied force less than μ_s N; asks for friction force Trap: Answering μ_s N without checking if $F_{applied}$ < μ_s N Strategy: Compare $F_{applied}$ with μ_s N. If less, $f_s$ = $F_{applied}$. If greater, body slides, use $f_k$.

Pattern 4: FBD on Inclined Plane (Numerical, 1 mark)

Frequency: Every year in some form Format: Block on rough incline; find acceleration or friction force Trap: Using N = mg instead of N = mg cos θ Strategy: Always resolve weight along and perpendicular to the incline first.

Pattern 5: Atwood Machine (Numerical, 1 mark)

Frequency: Moderate Format: Two masses on pulley; find acceleration or tension Strategy: Write equations for each mass separately. Add to eliminate T and find a. Substitute to find T.