1. IP2.12.6 Work and friction © Oxford University Press 2011 Work and friction

2. IP2.12.6 Work and friction © Oxford University Press 2011 When objects rub against each other, energy is transformed from kinetic energy into heat. We say that work is being done against friction.

3. IP2.12.6 Work and friction © Oxford University Press 2011  In most instances friction is bad.  It reduces the efficiency of devices and wastes energy because it transforms useful energy into wasted heat.  In an engine, oil is used to reduce friction so useful energy to power the car is not lost to the environment by wasted heat.

4. IP2.12.6 Work and friction © Oxford University Press 2011  Sometimes work done against friction can be very useful.  When a Formula 1 car brakes, friction is used to slow it down. Special materials are used so that a large amount of energy can be transferred to heat by friction in the brakes. These brake discs can reach temperatures in excess of 1000 °C. What energy transformation takes place when a car slows down in this way? Kinetic energy is transformed into heat energy.