## Overview This topic covers the relationship between work, energy and power. It develops the conservation of energy, and the link between work and energy via the work-energy relationship. ## Working Scientifically This unit contains opportunities for learners to apply scientific knowledge to practical contexts. ## Mathematical Skills There are a number of opportunities for the development of mathematical skills in this unit. These include recognising and making use of appropriate units in calculations; using expressions in decimal and standard form; using ratios, fractions and percentages; using calculators to find and use power functions; solving algebraic equations. ## How Science Works There are opportunities within this topic for learners to use theories, models and ideas to develop scientific explanations; to analyse and interpret data to provide evidence, recognise correlations and causal relationships. Learners can apply the principle of conservation of energy to many different situations, including investigating data to be able to compare the efficiency of power stations and the comparison of the different methods of generating electrical power and evaluate their impact on the consumer. ### Learners should be able to demonstrate and apply their knowledge and understanding of: (a) the idea that work is the product of a force and distance moved in the direction of the force when the force is constant (b) the calculation of the work done for constant forces, when the force is not along the line of motion ($\text{work done }= Fx \cos \theta$) (c) the principle of conservation of energy including knowledge of gravitational potential energy ( ) mg h , elastic potential energy 1 2 2 ( ) kx and kinetic energy 1 2 2 ( ) mv (d) the work-energy relationship: 1 1 2 2 Fx mv mu 2 2 = − (e) power being the rate of energy transfer (f) dissipative forces for example, friction and drag cause energy to be transferred from a system and reduce the overall efficiency of the system (g) the equation efficiency = useful energy transfer total energy input × 100%