Physics
Physics on this paper covers mechanics, fluids, electricity, waves and optics, and basic thermodynamics. It rewards correct unit handling and clean algebraic manipulation more than memorised formulas.
Core rules
- Kinematics: v = u + at, s = ut + ½at², v² = u² + 2as; horizontal and vertical projectile motions are independent.
- Newton's second law ΣF = ma; static friction satisfies f ≤ μN; circular motion needs a = v²/r toward the centre.
- Conservation of energy and momentum; distinguish elastic (kinetic energy conserved) from inelastic collisions.
- Fluids: P = P₀ + ρgh; continuity A₁v₁ = A₂v₂; Poiseuille flow Q = πΔP r⁴/(8ηL).
- Circuits: V = IR; series resistances add, parallel conductances add; capacitors Q = CV and energy = ½CV².
- Waves and optics: v = fλ; Snell n₁sin θ₁ = n₂sin θ₂; total internal reflection beyond the critical angle.
Worked example
A 6 Ω and a 3 Ω resistor are connected in parallel across a 12 V battery of negligible internal resistance. Find the total current. Parallel equivalent: 1/R = 1/6 + 1/3 = 1/2, so R = 2 Ω. Total current I = V/R = 12/2 = 6 A, split as 2 A through the 6 Ω and 4 A through the 3 Ω. The smaller resistor carries the larger current, and both branches see the full 12 V.
Traps
- Substituting mass for weight, or leaving grams and centimetres in SI equations.
- Adding parallel resistors as if in series.
- Using degrees in expressions derived for radians.
- Applying Bernoulli to a viscous or turbulent flow where its assumptions fail.