Well... I really meant I am not telling
yet 
!
The authors of FLP chose to include answers in Caltech's
Exercises for FLP, Vol. I, because those exercises are for freshmen. The freshmen were expected to attempt solving each exercise
without looking at the answer first. After they came up with their own answer they were free to compare it with the published one in the back of the book - if those differed significantly, then, armed with knowledge of the correct answers, the student could at least seek correct solutions.
However, the exercises in Caltech's
Exercises for FLP, Vol. II and Exercises for FLP, Vol. III are for (presumably more advanced, and more able) sophomores who were expected to solve problems without any knowledge of the answers, so the answers to the Vols. II & III exercises were never published. (BTW, the ideas for about half of the Vol. II exercises and three-quarters of the Vol. III exercises originated with Feynman himself.) Solutions to these exercises were recorded in notebooks kept by the Caltech teachers who taught the FLP course during the decade that FLP was used as the Introductory Physics textbook at Caltech (a 2-year course required by all students). And now, due to popular demand, Caltech is allowing my colleagues and I to publish the answers (and also a sprinkling of example solutions) to
all the exercises. The exercises (and answers) will be included in a greatly expanded edition of
Feynman's Tips on Physics, a problem-solving supplement to The Feynman Lectures on Physics (TIPS).
The new edition of TIPS will be published in the same format as FLP Vols. I-III; it will include all the material that was included in the first edition (four Feynman lectures - three on problem-solving and one on dynamical systems and their applications (primarily inertial guidance) - and an historical essay by FLP coauthor Matt Sands about the origins of FLP); In addition it will include all exercises in
Exercises in Elementary Physics (EIP) by Leighton and Vogt, and in Caltech's
Exercises for FLP, Vol. II and Vol. III.
Note: EIP is (more or less) a superset of
Exercises for FLP, Vol. I, and both were published with answers, which we are copying unchanged, except where they were originally misprinted, whereas the answers (and solutions) for the Vols. II & III exercises will be new. All the figures will be redrawn as well. I can't tell you exactly when the second edition of TIPS will be published, because I don't know yet - there are a number of mitigating factors - but I am hoping it will be sometime this year.
Mike Gottlieb
Editor, The Feynman Lectures on Physics
Coauthor, Feynman's Tips on Physics