Trail · 3 stops

Why do things stop moving?

A rolling ball stops, a sliding box stops, a plane needs engines to keep going. Three stops explain the forces that slow everything down.

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1. 1
   Newton's Laws of Motion

   Three rules that explain how every object moves: inertia, force equals mass times acceleration, and every action has an equal and opposite reaction.

2. 2
   Friction

   The force that resists surfaces sliding over each other. Why it exists, why starting is harder than keeping going, and how we use it or fight it.

3. 3
   Drag

   Drag is the air resistance that pushes back on anything moving through air. Its strength depends on shape, surface, speed and the air itself.