AP Physics 1 & 2 Newton's 3rd Law of Motion
II. Mechanics: Lecture 7 | 5:58 min
Previously we mentioned that everything with mass has a constant acceleration in the y-direction, but that we arent falling through the Earth. This is because of Newtons 3rd law, which states that for every action there is an equal and opposite reaction. The chair youre sitting in is actually exerting an upward force on you to counteract the gravitational force. Think about this for a second: despite having no net velocity relative to the Earth, you are accelerating. The reason we dont realize it is because of Newtons 3rd law, which causes no velocity to be produced from our acceleration (assuming youre standing on something). The next topic is one that would cause the entire world to literally collapse if absent.