200 puzzling physics

200 Puzzling Physics Problems

P. Gnadig

Eotvos University, Budapest

G. Honyek

Radnoti Grammar School, Budapest

K. F. Riley

Cavendish Laboratory, Fellow of Clare College, Cambridge

11111~11111 CAMBRIDGE::: UNIVERSITY PRESS

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© Cambridge University Press 2001

This book is in copyright. Subject to statutory exceptionand to the provisions of relevant collective licensing agreements,

no reproduction of any part may take place withoutthe written permission of Cambridge University Press

First published 2001Reprinted 2002, 2003

Printed in the United Kingdom at the University Press, Cambridge

Typeface Monotype Times 10/13 pt System ~TEX [UPH]

A catalogue record for this book is available from the British Library

Library 0.( Congress Cataloguing in Publication dataGnadig, Peter, 1947-

200 Puzzling Physics Problems I P. Gnadig, G. Honyek, K. F. Riley.p. ern.

Includes bibliographical references and index.ISBN 0 521 77306 7 - ISBN 0 521 77480 2 (pb.)

1. Physics-Problems, exercises, etc. I. Title: Two hundred puzzling physics problems.II. Honyek, G. (Gyula), 1951- III. Riley, K. F. (Kenneth Franklin), 1936- IV. Title.

QC32.G52 2001530'.076-dc21 00-053005 CIP

ISBN 0 521 77306 7 hardbackISBN 0 521 77480 2 paperback

Contents

PrefaceHow to use this bookThematic order of the problemsPhysical constantsProblemsHintsSolutions

page VII

X

Xl

xiii1

5069

Preface

In our experience, an understanding of the laws of physics is best acquiredby applying them to practical problems. Frequently, however, the problemsappearing in textbooks can be solved only through long, complex calcu­lations, which tend to be mechanical and boring, and often drudgery forstudents. Sometimes, even the best of these students, the ones who possessall the necessary skills, may feel that such problems are not attractive enoughto them, and the tedious calculations involved do not allow their 'creativity'(genius?) to shine through.

This little book aims to demonstrate that not all physics problems are likethat, and we hope that you will be intrigued by questions such as:

• How is the length of the day related to the side of the road on whichtraffic travels?

• Why are Fosbury floppers more successful than Western rollers?

• How far below ground must the water cavity that feeds Old Faithfulbe?

• How high could the tallest mountain on Mars be?• What is the shape of the water bell in an ornamental fountain?

• How does the way a pencil falls when stood on its point dependupon friction?

• Would a motionless string reaching into the sky be evidence forUFOs?

• How does a positron move when dropped in a Faraday cage?• What would be the high-jump record on the Moon?• Why are nocturnal insects fatally attracted to light sources?

• How much brighter is sunlight than moonlight?• How quickly does a fire hose unroll?

VB