But now drop the apple on Newton in the open air. Gravity’s force, of course, doesn’t change. But the faster the apple falls, the greater the resistance of the air pushing back against it. The apple’s acceleration now depends on both the gravity speeding it up and the air resistance slowing it down, which in turn depends on the apple’s speed at any moment, which in turn is changing every fraction of a second. That is the kind of problem that calls for a more-than-ordinary brain.
