CONTENTS
What is a force? 6
Elastic forces 9
Gravitational forces 12
Impact forces and pressure 18
Cohesive forces 24
Electric and magnetic forces 32
Muscular forces 36
Forces due to light pressure 38
Summary and conclusions 40

This book is one in a series of physics background books
intended primarily for use with the Nuffield O-Level Physics
Project. The team of writers who have contributed to the series
were all associated with that project. It was always intended
that the Nuffield teachers' materials should be accompanied
by background books for pupils to read, and a number of such
books is being produced under the Foundation's auspices.
This series is intended as a supplement to the Nuffield pupils'
materials: not books giving the answers to all the investigations
pupils will be doing in the laboratory, certainly not textbooks
in the conventional sense, but books that are easy to read and
copiously illustrated, and which show how the principles
studied in school are applied in the outside world.
The books are such that they can be used with a conven-
tional as well as a modern physics programme. Whatever
course pupils are following, they often need straightforward
books to help clarify their knowledge, and sometimes to help
them catch up on any topic they have missed in their school
course. It is hoped that this series will meet that need.
This background series will provide suitable material for
reading in homework. This volume is divided into sections,
and the teacher may feel that one section at a time is suitable
for each homework session for which he wishes to use the
book.
This particular book is written as a background book for the
Forces section of Years I and, more particularly, II. It is hoped
that the examples given, which range rather beyond the Nuffield
course, will help pupils to appreciate the importance of forces
in everyday life and begin to explain how they come about,
thus laying the foundation for more formal studies later. At
the same time, some attention is paid to the role of forces in
technology and engineering. This is essentially a book for
pupils to browse in, taking up points which catch their interest
and possibly pursuing them further.