Unit 6

We went over Newton's Third Law of Motion that says for every force, there is an equal and opposite force, having an equal magnitude but going in the opposite direction. This is called Action Reaction. So for example, sitting in a chair. When you sit on a chair, both you and the chair are at rest. Your mass and weight is pushing down while the chair pushes up with the same amount of force. If it is unable to return the same amount of force, the chair breaks! When it breaks, you end up falling and accelerating downwards towards the floor. This can be turned into a free body diagram using the letters N  to represent "Normal" because it can contact with the surface, and mg to represent weight, so there would be two equal vectors. The mg vector will be pointing south and the N vector north, making it balanced. Free body diagrams don't show if an object is moving, but can show if it is accelerating.

If i were to break my chair, my body would accelerate down with constant velocity and keep increasing speed. Ignoring air resistance, my free body diagram would be unbalanced and be just a vector pointing down and have only weight as the south-pointing vector.