This is the third chapter of the book "The Nature of Code" about friction and resistance, I don't know what the problem is, as a beginner this is my first problem I can't solve, so I ask you for help.THANKS！

Processing Beginners
2

Hello,

The answer is here:
https://natureofcode.com/book/chapter-2-forces/

The chapter tells you which class to put the functions in.

:)