Law 2

  The acceleration of a body is directly proportional to the net force on it and inversely proportional to it's mass. F=ma

  A net force on an object causes it to accelerate. In addition, the larger the mass of the object, the smaller the acceleration. For this reason, we say that a massive body has more inertia than a less massive body.
  Lay an index card over a drinking glass. Place a penny on the center of the card. With the flick of a finger, give the card a quick horizontal push. The card moves away, but the penny drops into the glass. The penny doesn't accelerate with the card because the penny has more mass and a horizontal force is needed to accelerate it. The card is too smooth to exert much horizontal force on the penny. With little horizontal force on it, the penny has little sideways acceleration. As soon as the card is no longer under it, the upward force of the card is removed. There is mostly a net downward force, the force of gravity, so the penny accelerates downward, falling into the glass.

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