Ibhanan Kulkarni
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  1. Inertia. An object at in motion will stay in motion unless an external force acts upon it, and an object at rest will stay at rest unless an external force acts upon it. Example: A ball rolling and hitting a wall. The ball is in motion and stays in motion until an external force (the wall) is exerted upon it. Similarly, when a ball is at rest, and you push it, it wall start moving because an external force (your push) was exerted upon it.
  2. F=ma. The amount of force exerted on an object is equal to its mass times its acceleration. Example: The force acting upon a ball that has a mass of 10kg and is accelerating at 10 m/s is 100 N (Newtons).
  3. For every action, there is an opposite and equal reaction. If there is a force acting upon an object from the left, then there will also be a force that will act upon the object from the right. Example: In the rolling ball example mentioned above, the action is the ball rolling towards the wall and the reaction is the wall exerting the same force as the ball exerts on the wall when the ball hits the wall.