1. Forces Act in Pairs
2.3 Outline

2. I. Newton’s third law relates action and reaction forces
Newton’s third law: for every action there is an equal and opposite reaction
example: a jellyfish applies a force down, the water pushes back

3. A. Action and Reaction Pairs
action/reaction force pair is known as the force that is exerted on an object and the force that the object exerts back
action and reaction forces do not always result in motion; for example if you press down on a table, the table pushes back with the same force, but there is no motion

4. B. Action and Reaction Forces Versus Balanced Forces
balanced forces act on a single object
example: if two friends pull on opposite sides of backpack with same force, no motion... BALANCED

5. B. Action and Reaction Forces Versus Balanced Forces (cont.)
action/reaction forces act on different objects
example: when dragging a heavy backpack, the backpack pulls back on you with equal and opposite force

6. II. Newton’s three laws describe and predict motion
Newton’s three laws can explain the motion of almost any object
the three laws are not independent of one another; they are used together to explain the motion of objects

7. II. Newton’s three laws describe and predict motion
Newton’s laws can be used to make predictions about motion
if you know the force acting on an object, then you can predict how that object’s motion will change