The parts of the question that were problematic for the candidates were parts (a) and (c). The required responses to these parts are given below:
(ai) - asbestos;
- synthetic resin of phenol – formaldehyde;
- Kevlar fibre.
(aii) - high coefficient of friction when used with steel;
- ability to resist wear;
- ability to resist heat;
- ability to resist moisture;
- high fensile strength to resist high stress imposed during
severe braking.
(aiii) - riveting
- bonding.
(c) When the driver depresses the brake pedal, fluid from the master cylinder flows through the check valve into the wheel cylinder.
This causes the piston in the wheel cylinder to move out causing the shoes to contact the brake drum thus stopping the vehicle.
