OCR AS Level Physics A Past Papers

SUVAT questions require identifying which four of the five variables (s, u, v, a, t) are given or can be calculated, then selecting the equation that contains those variables. The five standard equations must be memorised, as they are not always provided in the booklet in exactly the form needed. For projectile motion, resolve the problem into horizontal and vertical components: horizontal acceleration is zero (constant velocity), vertical acceleration is g downwards (9.81 m s⁻²). Treat each component independently and use the same time of flight in both. For electrical circuit questions, always apply Kirchhoff's laws systematically. Kirchhoff's First Law (KCL): the sum of currents entering a junction equals the sum of currents leaving it (conservation of charge). Kirchhoff's Second Law (KVL): the algebraic sum of EMFs in any closed loop equals the algebraic sum of potential differences across the resistors in that loop (conservation of energy). For potential divider calculations: the voltage across a component in a potential divider is proportional to its resistance as a fraction of total resistance — Vout = Vin × (R₂/(R₁ + R₂)). The photoelectric effect is frequently assessed at AS Level and requires precise terminology. Light below the threshold frequency cannot eject photoelectrons, regardless of intensity — this is because each photon interacts with one electron and must have sufficient energy (hf ≥ φ, where φ is the work function) to liberate it. Increasing intensity below the threshold frequency only increases the number of photons arriving per second, not their individual energies. Above the threshold frequency, the maximum kinetic energy of ejected electrons is EK(max) = hf − φ — this is independent of intensity and increases linearly with frequency.