Physics
The physics paper is school level: concepts plus short numericals, mostly mechanics, with some heat, waves, light and electricity. Marks come from the correct formula, correct substitution and correct unit, in that order.
Core content
- Kinematics: v = u + at; s = ut + ½at²; v² = u² + 2as.
- Dynamics: Newton's three laws, F = ma, momentum p = mv and its conservation, friction.
- Work, energy, power: W = Fs cosθ, KE = ½mv², PE = mgh, P = W/t.
- Heat: Q = mcΔT for temperature change, Q = mL for change of state.
- Waves and sound: v = fλ; sound requires a medium, light does not.
- Light: laws of reflection, refraction, lens and mirror formulae.
- Electricity: V = IR, P = VI, series and parallel resistance, magnetic effect of current.
Worked example
A car starts from rest and accelerates at 2 m/s² for 5 s. Find its final speed and the distance covered.
Reasoning: u = 0, a = 2 m/s², t = 5 s. Then v = u + at = 0 + (2)(5) = 10 m/s, and s = ut + ½at² = 0 + ½(2)(25) = 25 m. Self-check with v² = u² + 2as: 100 = 0 + 2(2)s, so s = 25 m. Two formulas giving the same distance is a strong signal that the working is right.
Traps
- Speeds given in km/h must be converted: divide by 3.6.
- Mass in kilograms is not weight in newtons; use W = mg.
- In parallel, 1/R = 1/R₁ + 1/R₂, so the total is smaller than the smallest resistor.
- Deceleration is negative acceleration; keep signs consistent throughout.
- Writing the formula but omitting the unit loses marks in numericals.
- Confusing frequency with time period: f = 1/T.