Unit 2 covers forces and Newton\'s laws — the tools for analysing why objects move (or don\'t). Free body diagrams and F = ma form the core problem-solving framework.
First law: an object remains at rest or moves with constant velocity unless acted upon by a net external force (inertia). Second law: ΣF = ma (vector equation). Third law: if A exerts force on B, B exerts equal and opposite force on A (same type of force, different objects). Mass vs weight: W = mg. Normal force: perpendicular to surface. Tension: along rope/string. Free body diagrams: isolate object, draw all forces acting ON it.
Friction: fₛ ≤ μₛN (static, up to maximum), fₖ = μₖN (kinetic, constant). Inclined plane: resolve weight into components parallel (mg sinθ) and perpendicular (mg cosθ). Atwood machine: two masses over pulley. Apply F = ma to each mass; acceleration = (m₁-m₂)g/(m₁+m₂). Circular motion: net force directed toward centre (centripetal force) = mv²/r. This is not a new force — it\'s the resultant of existing forces (gravity, tension, normal, friction).
Centripetal force is NOT a separate force — it\'s the name for the net force that points toward the centre of a circular path. It\'s always caused by real forces: gravity (satellite orbiting Earth), tension (ball on a string), friction (car turning), normal force (loop-the-loop). On a free body diagram, never draw "centripetal force" as a separate arrow. Instead, identify which actual forces provide the centripetal acceleration. Set the net inward force equal to mv²/r to solve problems.
Book a Trial + Diagnostic session. Get a personalized Learning Path with clear milestones, tutor match, and a plan recommendation — all within 24 hours.
Book Trial + Diagnostic →