We come to the runway and start our takeoff roll.
After about 4 secs, the plane starts braking, and soon stops.
Believe me, we DID move. I start counting seconds from the moment the plane started moving, rather that from the engine spool. Of course, I did not count the seconds, so it is my estimation. The (first) braking itself took much more than 10 or 20 meters...
which is it?
4 seconds and start braking, or take 20 meters to stop?
because physics would require going significantly faster than you could achieve after 4 seconds of acceleration if it required 20 meters to stop.