Classical Mechanics

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Pushing a Chair Across the Floor


You shove a chair with wheels (and let it go) and it starts moving across the floor. However, the chair soon slows down and comes to a complete stop. To keep the chair moving, you need to keep pushing on it. This simple experiment implies that


Newton's first law, or the law of inertia, does not apply to a chair moving horizontally.


the action-reaction forces act on the chair and cancel each other.


a net force in the direction opposite to the motion of the chair acts to slow it down.


the weight of the chair slows it down.