Below you can find the Newton's third law of motion explains why this 6-letter reaction happens after you fire a gun Jeopardy Words Answer. The answer to Newton's third law of motion explains why this 6-letter reaction happens after you fire a gun has 6 letters. This clue belongs to the Reruns category and is part of Jeopardy Word Level 463. If you scroll near the bottom you will find other clues and answers part of level 463