Wilczek replies: Ramamurthy Ravi’s letter is an excellent, scholarly supplement to my October column, which emphasizes that some classical masters of mechanics had logical and aesthetic misgivings about the force concept, even before modern physics began to push us strongly toward different ones.
Regarding Brent Meeker’s letter, my critique was meant to be directed at foundational issues including, specifically, which principles should be regarded as primary, and which as derived. There are some significant problems with using F = ma as a primary principle, as I discussed. They could be avoided, perhaps advantageously, by focusing on momentum and energy. Of course, in that approach it would still be appropriate and extremely useful to have F = ma as a derived equation, with its limitations indicated. Some intellectual inertia isn’t necessarily a bad thing, if it keeps you moving in the right direction and allows you to remain in sync with long-established flows.
