Available practice: 73 of 75 marks. Parts 7(a) await marking support. Scores cover available parts only. Theory Paper 2: Section A is compulsory and Section B offers a choice of two questions. Four published mark-scheme discrepancies across the two variants are held from automatic marking.
(a)The overall stopping distance of a cyclist is made up of two parts, as shown in Fig. 12.1: • the distance the cyclist travels during the reaction time of the cyclist (the thinking distance) • the distance the cyclist travels after the brakes are applied (the braking distance) State the energy change that occurs during braking.
[2 marks]
(b)(i)The overall stopping distance of a cyclist is made up of two parts, as shown in Fig. 12.1: • the distance the cyclist travels during the reaction time of the cyclist (the thinking distance) • the distance the cyclist travels after the brakes are applied (the braking distance) A ball rolls in front of a cyclist at time t = 0 and the cyclist brakes and comes to rest. Fig. 12.2 shows the speed-time graph for the cyclist. Using Fig. 12.2, determine the reaction time of the cyclist.
Answer guidance
Using You must use the thing it names. An answer that reaches the right value another way may not score.
[1 mark]
(b)(ii)The overall stopping distance of a cyclist is made up of two parts, as shown in Fig. 12.1: • the distance the cyclist travels during the reaction time of the cyclist (the thinking distance) • the distance the cyclist travels after the brakes are applied (the braking distance) A ball rolls in front of a cyclist at time t = 0 and the cyclist brakes and comes to rest. Fig. 12.2 shows the speed-time graph for the cyclist. Using Fig. 12.2, calculate the thinking distance.
Answer guidance
Using You must use the thing it names. An answer that reaches the right value another way may not score.
[2 marks]
(b)(iii)The overall stopping distance of a cyclist is made up of two parts, as shown in Fig. 12.1: • the distance the cyclist travels during the reaction time of the cyclist (the thinking distance) • the distance the cyclist travels after the brakes are applied (the braking distance) A ball rolls in front of a cyclist at time t = 0 and the cyclist brakes and comes to rest. Fig. 12.2 shows the speed-time graph for the cyclist. State how the braking distance is found using Fig. 12.2.
Answer guidance
State A short answer. No explanation is needed, and adding one cannot earn extra marks.
[1 mark]
(b)(iv)The cyclist in Fig. 12.2 travels initially at 5.0 m/s when a ball rolls in front at t = 0. Reaction time and deceleration are unchanged from Fig. 12.2. Draw the new speed–time graph.
Answer guidance
Draw Accuracy is being marked. Use the figure and be precise about position and labels.
[2 marks]
(b)(v)The cyclist in Fig. 12.2 has a longer braking distance on a wet road. Explain why the wet surface increases that distance.
Answer guidance
Explain Give reasons, not just what happens. Each distinct reason is usually worth a mark.
[3 marks]
(c)(i)In the hydraulic bicycle brake of Fig. 12.3, pressure in the oil rises by 1.2 × 10⁶ Pa and piston R has area 5.0 × 10⁻⁵ m². Calculate force F on piston R.
Answer guidance
Calculate Show your working. The method can earn marks even when the final value is wrong, and a bare answer often cannot.
[2 marks]
(c)(ii)In the hydraulic bicycle brake of Fig. 12.3, the force on each brake pad exceeds force F on piston R. Explain why.
Answer guidance
Explain Give reasons, not just what happens. Each distinct reason is usually worth a mark.
[2 marks]
5054/21/M/J/16Cambridge O Level Physics 5054 · May/June 2016 · Paper 2 variant 1 · Question 12