This book has been written to help you get through the core unit Mechanical Principles and a further five optional units which may form part of your BTEC National Certificate or Diploma award in mechanical engineering. It accompanies the book BTEC National Engineering by Mike Tooley and Lloyd Dingle and provides the essential underpinning knowledge required by a student who wishes to pursue a career in mechanical engineering. The book has been written by a highly experienced lecturer with over thirty years experience of industry and higher education. It has been designed to cover the requirements of the revised and updated BTEC Engineering programme. The author has adopted a common format and approach throughout the book with numerous student activities, examples, problems and key points.