Figure 5. This is an example of an action. This airplane is experiencing movement.
"For every action, there is an equal and opposite reaction."
"For every action1"
Action means some change or movement.
This part just means that the following part(s) apply to every change/movement.
Figure 5. This is an example of an action. This airplane is experiencing movement.
"there is an equal and opposite reaction2"
A reaction is an action happening because of an action. An equal and opposite reaction means if object A and object B collide,
then object A hits object B with the same force object B hits object A.
Figure 6. This image shows how equal and opposite
reactions look like when pushing on a wall.
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1: Action -- Any movement/change in position.
2: Reaction -- A response to an event, in other words an action because of another action.