Physics: Principles, Formulas, and Common Pitfalls
What the Kankor physics section rewards
Physics items test conceptual understanding plus the ability to select and apply the right formula. Core areas: kinematics, Newton's laws and forces, work, energy and power, momentum, circular motion and gravitation, fluids and pressure, heat and thermodynamics, waves and sound, geometric optics, electricity and magnetism, and simple circuits.
Concepts you must own
- Kinematics: v = u + at, s = ut + ½at², v² = u² + 2as; distinguish speed from velocity and distance from displacement.
- Dynamics: F = ma, friction f = μN, and free-body diagrams.
- Energy: conservation of mechanical energy; power P = W/t.
- Momentum: p = mv; conservation in collisions.
- Circular motion: centripetal force F = mv²/r.
- Ohm's law and circuits: V = IR; series and parallel resistance rules; electrical power P = VI.
- Optics: reflection and refraction, Snell's law n₁sinθ₁ = n₂sinθ₂.
Traps that appear
- Direction and sign conventions - acceleration opposite to motion means slowing down.
- Forgetting to convert units (grams to kilograms, cm to m) before substituting.
- Confusing mass and weight (w = mg).
- Mixing series and parallel rules for resistors.
- Using total distance instead of displacement in work calculations when force is not along the path.
Rule of thumb
Write the known quantities with units, state the unknown, then choose the formula that contains exactly those symbols. Worked example: a 2 kg object accelerates from rest at 3 m/s² for 4 s. Final velocity v = 0 + 3×4 = 12 m/s; distance s = ½×3×4² = 24 m; kinetic energy = ½×2×12² = 144 J. Each step uses only one formula, which keeps sign and unit errors visible.