This is the first of a three-book course written to adequately cover the new NERDC curriculum for Senior Secondary School Physics, providing theory, laboratory work and evaluation exercises, including multiple-choice questions, in each chapter. The series has also been designed to meet the needs of students writing SSCE in Nigeria and all other West African countries as well as NECO and UTME examinations. Although Year 1 students of the Senior Secondary School have studied Basic Science at the Junior Secondary School, we have found it necessary to include here some Junior Secondary School topics, mainly as revision exercises, which will enhance their knowledge of new topics. For this reason, measurement is treated in this book, as we believe that this topic is fundamental to the successful study of Physics.