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) [Figure 12.1 (not to scale)]

1. (a)State the energy change that occurs during braking.[2]
2. (b)(i)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. [Figure 12.2] Using Fig. 12.2, determine the reaction time of the cyclist.[1]
3. (b)(ii)Using Fig. 12.2, calculate the thinking distance.[2]
4. (b)(iii)State how the braking distance is found using Fig. 12.2.[1]
5. (b)(iv)On another occasion, the same cyclist travels at an initial speed of 5.0m/s. A ball rolls in front of the cycle at time t = 0. The cyclist has the same reaction time and the deceleration of the cycle is the same as in Fig. 12.2. On Fig. 12.2 draw the new speed-time graph for the cyclist.[2]
6. (b)(v)The braking distance is longer when the cyclist stops on a wet road. Explain why.[3]
7. (c)(i)Fig. 12.3 shows the hydraulic braking system of the cycle. [Figure 12.3 (not to scale)] The cyclist applies a force on the brake lever. This increases the pressure in the oil by 1.2 x 10⁶ Pa. The cross-sectional area of piston R is 5.0 × 10⁻⁵ m². Calculate the force F applied by the brake lever to piston R.[2]
8. (c)(ii)The force applied to each of the brake pads is larger than F. Explain why.[2]

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