There are many different kinds of forces: gravity, wind, magnetic, elastic, frictional, the static support force, atomic forces. Our muscles are also capable of exerting forces, which is where we get the concept of a force as being a "pushing or a pulling." It is also apparent that forces are in some way connected with motion.

The view of Aristotle was that: The natural state of an object is to be at rest. An object moves only when a force acts on it.

According to the Law of Inertia or Newton's first law: An object at rest stays at rest unless acted upon by a net external force. An object moving at a constant speed will continue to move at that speed unless acted on by a net external force.

Working in groups of two, three or four draw a force diagram for the following experiments. Write down your OBSERVATIONS, not inferences. Comment on whether your observations conform or do not conform with the Aristotelian view and the Newtonian view.

  • Experiment #1: Free fall.
  • Experiment #2: Object resting on a table.
  • Experiment #3: Ball rolling on a table at constant speed.
  • Experiment #4: An object is resting on a table. The object is pushed but does not move.
  • Experiment #5: An object is dragged across the table at a constant speed against the force of friction.