I would like to thank the following:

Mr. R. Sulley, Commissioning Editor, Heinemann Educational Boleswa Publishers Ltd, Gaborone, Botswana for giving me initial direction in my work on the manuscript;

Mr. Mathew Flynn, Editor Engineering and Science, McGraw-Hill Book Company, Europe for assessing my work and encouraging me to continue it, as: "this book could be a great success";

Prof. J.S. Nkoma, Dean Faculty of Science, University of Botswana, Gaborone for his correction of the manuscript; ;

Dr. L. Molema, English Department, University of Botswana, Gaborone for patiently proof- reading the manuscript;;

Prof. M. Kahn, Professor of Science, Mathematics and Technology Education, University of Cape Town, South Africa for his constructive criticism; ;

Dr. N.M. Mawande, Head of Pre-Entry Science Department, University of Botswana for his permission to quote PESC binder and Laboratory Manual coordinated and edited by J. Andringa and B. Robinson respectively;

Prof. George Marx, past president, Eötvös Physical Society, Budapest and president of GIREP (International Research Group on Physics Teaching), for his encouraging comments;

Dr. T. Kreuels, Germany, for his editorial contribution; Mrs. C. Palmer-Person, USA for her critical remarks and advice concerning publishing;;

Mr. N. Csomos, Hungary and A. du Plessis, RSA for patiently retyping the manuscript; Mr. J. Flisak, Poland, Ms. S. Toth and Ms. T. Soos, Hungary for their drawings;;

Australian Post Office for their stamps commemorating metric conversion; ;

Ms. Adele van Zyl, my present webmaster, Chidori Designs, George, South Africa for the website design. As Minerva Press, London, UK "lost" the electronic form of the book (first edition 1999, 162 pages), the text was retyped by Mrs. Angelique du Plessis from Drukkor Printing, George and edited by Mrs. Wilma Venter, George, South Africa. Thank you for your wonderful work and cordial assistance.

I would like to express my special gratitude to: Dr. Orlando Hall Rose, Chief Science and Technology Education UNESCO, Paris; Prof. John L. Hubisz, Book Reviews, "The Physics Teacher" journal, President North Carolina State University; Prof. George Marx, past President Eötvös Physical Society, Budapest; Prof. Rita Serafini, Associazione per I'Insegnamento della Fisica, Italy; Prof. D. Knoesen, University of Western Cape, South Africa; Prof. P.K. Jain, University of Botswana; Dr. Qwen Pilling, Salters Advanced Chemistry Project, University of York, UK; Prof. Andy Buffler, University of Cape Town and Dr. P. Horn, CSIR, South Africa for their favourable reviews. Many thanks to Mrs. Lorelle Young, President US Metric Association, Mrs. Valerie Antoine, Executive Director USMA for their permission to quote their answers to questions regarding the introduction of metric system in USA and Dr. Don Hillger, USMA for his corrections; the interview with Mrs. Antoine and the reviews, I am enclosing on the last pages of the book.

NB.: The copies of the first edition of the book published by infamous Minerva Press and sold by Amazon, Barnes and Noble, Barns International and others, as well as those translated to Portugese and Hindi, have been sold without my permission.

The author welcomes criticism, comments and suggestions from teachers, students and other readers for improvement of further editions of this book.