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Energy in a system can be changed, in particular by mechanical work. It cannot be created or destroyed but it can be transferred, dissipated or stored in different ways.

The rate at which energy is transferred is called power and the amount of energy that is usefully transferred is called efficiency. It is important to be able to calculate power and efficiency.

Understanding how to approach exam questions helps to boost exam performance. Questions will include multiple choice, structured, using mathematical skills and extended writing.