Mark Scheme

Section A — Structured Questions

1. (a) F = ma = 900 × 2.5 (M1 M1) = 2250 N (A1). [3] (b) Any two: higher speed; worn brakes/tyres; wet/icy road (less friction); greater mass/load; driver reaction (thinking distance) — accept factors that increase braking (stopping) distance. [2] (c) (up to 4) At first the weight (gravity) is greater than air resistance, so the skydiver accelerates; as speed increases, air resistance increases; eventually air resistance equals the weight, so the resultant force is zero; with no resultant force there is no acceleration, so the velocity stays constant (terminal velocity). [4]

2. (a) GPE = mgh = 0.5 × 10 × 8 (M1 M1) = 40 J (A1). [3] (b) By conservation of energy, KE at the bottom = GPE at the top = 40 J (M1). ½mv² = 40 → v² = (2 × 40)/0.5 = 160 → v = √160 = 12.6 m/s (M1 M1 A1). [4] (c) (up to 2) Some energy is transferred to the surroundings (to the air/thermal energy) by air resistance/friction, so less energy is transferred to kinetic energy and the speed is lower. [2]

3. (a) R = V/I = 12 / 0.5 (M1 M1) = 24 Ω (A1). [3] (b) (up to 2) The total resistance in parallel is less than in series (less than the smallest individual resistance), because there are more paths for the current. [2] (c) P = VI = 12 × 0.5 = 6 W (M1 A1); energy = P × t = 6 × 120 = 720 J (M1 A1). [4]

4. (a) λ = v/f = 340 / 400 (M1 M1) = 0.85 m (A1). [3] (b) Order of increasing frequency: radio waves, visible light, gamma rays (M1 A1); use of radio waves — e.g. broadcasting/communications/TV (A1). [3] (c) (up to 3) Refraction = the change in direction of a wave as it passes from one medium into another; it is caused by the wave changing speed as it enters the different medium (the wavelength changes, frequency stays the same). [3]

5. (a) E = mcΔT = 2 × 4200 × 15 (M1 M1) = 126,000 J (M1 A1). [4] (b) (up to 4) In a solid, particles are close together in a fixed, regular arrangement and can only vibrate in place; in a gas, particles are far apart, arranged randomly, and move quickly in all directions. Two clear contrasts (arrangement + movement). [4]

Section B — Extended Response

6. (a) (up to 4) The gas particles move quickly and randomly; they collide with the walls of the container; each collision exerts a force on the wall; the total force from many collisions per second over the area of the wall produces the pressure. [4] (b) (up to 6) At constant temperature, pressure × volume is constant (P₁V₁ = P₂V₂): P₂ = (P₁V₁)/V₂ = (100 × 0.020)/0.008 (M1 M1) = 2.0/0.008 = 250 kPa (A1). Explanation (up to 3): reducing the volume means the same number of particles are in a smaller space, so they hit the walls more often (more collisions per second per unit area), which increases the pressure. [6]

7. (up to 6) Indicative content, for a chosen renewable (e.g. wind, solar, hydroelectric):

• How it generates electricity: e.g. wind turns turbine blades connected to a generator; or moving water (hydro) turns a turbine; or solar cells convert light directly to electricity.
• Advantage vs fossil fuels: renewable/will not run out; produces no carbon dioxide at the point of generation, reducing pollution/climate change.
• Disadvantage vs fossil fuels: unreliable/intermittent (depends on wind/sun) or high initial cost, visual/land impact. Levels: 5–6 = clear description + balanced advantage and disadvantage; 3–4 = some description with one comparison; 1–2 = basic. [6]

Sample Answers with Examiner Commentary

Question 2(b) — Sample Answers

Grade A response. "By the conservation of energy, all the gravitational potential energy is transferred to kinetic energy as the ball falls (ignoring air resistance). So the kinetic energy just before it hits the ground equals the GPE at the top, which is 40 J. To find the speed, I use KE = ½mv²: 40 = ½ × 0.5 × v², so v² = (2 × 40)/0.5 = 160, and v = √160 = 12.6 m/s."

Mark: 4/4. Examiner commentary: A model answer using the energy approach cleanly. The student states the key principle — GPE converts to KE, so KE = 40 J — then rearranges KE = ½mv² correctly to find the speed, showing each step. Rearranging to v² = 2KE/m before taking the square root is exactly the right method, and the arithmetic is accurate. Because the working is fully shown, every mark is secure.

Grade C response. "KE = 40 J because energy is conserved. Then v = 40 ÷ 0.5 = 80 m/s."

Mark: 2/4. Examiner commentary: The student correctly identifies that the kinetic energy is 40 J, earning the first marks, but then makes an error rearranging the kinetic energy equation. They appear to treat KE = mv rather than KE = ½mv², simply dividing by the mass. The correct method is v² = 2KE/m = (2 × 40)/0.5 = 160, then v = √160 = 12.6 m/s. Remembering the ½ and the square in KE = ½mv², and taking the square root at the end, would gain the remaining marks.

Question 6(b) — Sample Answers

Grade A response. "At constant temperature, pressure and volume are inversely proportional, so P₁V₁ = P₂V₂. Rearranging for the new pressure: P₂ = (P₁ × V₁) / V₂ = (100 kPa × 0.020 m³) / 0.008 m³ = 2.0 / 0.008 = 250 kPa. In terms of particles, squeezing the gas into a smaller volume means the same number of particles are now in a smaller space, so they collide with the walls more frequently — more collisions per second on each unit of area — and this increased rate of collisions is what raises the pressure."

Mark: 6/6. Examiner commentary: Full marks. The calculation is set out with the correct relationship (P₁V₁ = P₂V₂), a clear rearrangement, and an accurate answer of 250 kPa. Crucially, the student also gives the particle explanation the question asks for: a smaller volume means more frequent collisions with the walls per unit area, increasing the pressure. Linking the mathematical result to the particle model is exactly what earns the explanation marks, and many students give one without the other.

Grade C response. "P₂ = (100 × 0.020) / 0.008 = 250 kPa. The pressure goes up because the gas is squashed."

Mark: 4/6. Examiner commentary: The calculation is completely correct and clearly shown, earning the calculation marks, and the student knows the pressure increases. However, the particle explanation is too vague — 'the gas is squashed' states what happens without explaining why the pressure rises. The marks require the particle reasoning: in a smaller volume the particles hit the walls more often (more collisions per second per unit area), which increases the pressure. Adding that mechanism would gain the remaining marks.

Question 1(c) — Sample Answers

Grade A response. "When the skydiver first jumps, their weight (the force of gravity) is much greater than the air resistance, so there is a large resultant force downwards and they accelerate. As their speed increases, the air resistance acting upwards also increases. Eventually the air resistance grows until it is equal in size to the weight. At this point the two forces are balanced, so the resultant force is zero. With no resultant force there is no acceleration, so the skydiver continues to fall at a constant velocity — this is called terminal velocity."

Mark: 4/4. Examiner commentary: A full-mark answer that explains the whole process as a sequence of changing forces. The student correctly describes the starting situation (weight greater than air resistance, so acceleration), the change (air resistance increasing with speed), and the final balanced state (air resistance equal to weight, resultant force zero, no acceleration). Explicitly linking 'no resultant force' to 'no acceleration' and hence constant velocity is the key physics, and naming terminal velocity completes it. Answers that only state the forces are 'balanced' without the sequence tend to score lower.

Grade C response. "The skydiver reaches terminal velocity when the air resistance and the weight are balanced, so they stop accelerating and fall at a constant speed."

Mark: 2/4. Examiner commentary: The candidate correctly identifies the final balanced state — air resistance equal to weight, so no acceleration and constant speed — which earns two marks. However, the question asks the candidate to explain why the velocity becomes constant, and the answer jumps straight to the end without describing how the forces change to get there: at first the weight exceeds the air resistance (so the skydiver accelerates), and the air resistance then increases with speed until it equals the weight. Describing that build-up would gain the remaining marks.